diff --git a/PROJECT_DOCUMENTATION.md b/PROJECT_DOCUMENTATION.md
new file mode 100644
index 0000000..3154064
--- /dev/null
+++ b/PROJECT_DOCUMENTATION.md
@@ -0,0 +1,168 @@
+# Pen Tracker Project Documentation
+
+## Overview
+
+`pen-tracker` is a small Python package for tracking fountain pens and inks using CSV storage. It provides a single command-line interface (`pen-tracker`) for interactive data management, plus direct CLI commands for adding, listing, exporting, and maintaining the collection.
+
+This repository is structured as a standard Python package with source under `src/pen_tracker`, package metadata in `pyproject.toml`, and a small test suite under `tests`.
+
+## Key goals
+
+- Maintain a pen collection with fields such as make, model, nib, ink, purchase date, and notes.
+- Maintain an ink collection separately with vendor, name, color, purchase date, size, and notes.
+- Store data in CSV files for compatibility and simplicity.
+- Use a single CLI entry point for developer and automation workflows.
+
+## Repository layout
+
+- `pyproject.toml` — packaging metadata, dependencies, and entry points.
+- `README.md` — user-facing usage documentation.
+- `PROJECT_DOCUMENTATION.md` — developer/AI reference documentation.
+- `import_csv_to_sqlite.py` — standalone CSV-to-SQLite migration helper.
+- `src/pen_tracker/engine.py` — domain logic, data models, SQLite persistence, history tracking, and storage defaults.
+- `src/pen_tracker/cli.py` — command-line interface, interactive menus, and command parsing.
+- `tests/test_engine.py` — basic test coverage for core engine behavior.
+
+## Core components
+
+### `src/pen_tracker/engine.py`
+
+Primary responsibilities:
+
+- Define `Pen` and `Ink` dataclasses.
+- Provide `PenTracker` and `InkTracker` classes that:
+  - Decide storage path from environment or default XDG data directories.
+  - Load CSV files into Python objects.
+  - Normalize data on load.
+  - Persist sorted CSV output.
+
+Important details:
+
+- Default pen storage path: `~/.local/share/pen-tracker/pens.csv`
+- Default ink storage path: `~/.local/share/pen-tracker/inks.csv`
+- Environment overrides:
+  - `PEN_TRACKER_CSV` for pen storage.
+  - `INK_TRACKER_CSV` for ink storage.
+- `PenTracker.load_data()` maps CSV headers like `Date-Purchased` and `Current-Ink` to dataclass fields like `Date_Purchased` and `Current_Ink`.
+- CSV headers are written using the original hyphenated naming convention.
+
+### `src/pen_tracker/cli.py`
+
+Primary responsibilities:
+
+- Parse command-line arguments with `argparse`.
+- Provide commands for:
+  - `add` — add a new pen from CLI inputs.
+  - `list` — display all pens.
+  - `export` — export pens to JSON.
+  - `add-ink` — add a new ink.
+  - `list-inks` — list saved inks.
+- Provide an interactive text menu when no command is supplied.
+- Display one-based IDs for pens and inks.
+- Validate user input and dates.
+
+## Usage patterns
+
+### Installation
+
+```bash
+pip install .
+```
+
+### Run interactive CLI
+
+```bash
+pen-tracker
+```
+
+### Add a pen via CLI
+
+```bash
+pen-tracker add --make "Pilot" --model "Metropolitan" --nib "F"
+```
+
+### List saved pens
+
+```bash
+pen-tracker list
+```
+
+### Export pens to JSON
+
+```bash
+pen-tracker export --output my_pens.json
+```
+
+### Add an ink via CLI
+
+```bash
+pen-tracker add-ink --vendor "Diamine" --name "Majestic Blue" --color "Blue"
+```
+
+### List inks
+
+```bash
+pen-tracker list-inks
+```
+
+## Data model
+
+### Pen fields
+
+- `Make`
+- `Model`
+- `Date_Purchased` / `Date-Purchased`
+- `Vendor`
+- `Nib`
+- `Nib_Material` / `Nib-Material`
+- `Body`
+- `Cap`
+- `Post`
+- `Current_Ink` / `Current-Ink`
+- `Inked_date` / `Inked-date`
+- `Notes`
+
+### Ink fields
+
+- `Vendor`
+- `Name`
+- `Color`
+- `Purchased`
+- `Size`
+- `Notes`
+
+## Packaging and scripts
+
+The package is configured with `pyproject.toml` and uses `setuptools.build_meta` as the build backend. There are no runtime dependencies.
+
+Entry point:
+
+- `pen-tracker = pen_tracker.cli:main`
+
+## Developer notes
+
+- The CLI is the only supported interface. The repository no longer includes any TUI or graphical code.
+- Data is now persisted in SQLite, with default path `~/.local/share/pen-tracker/pen_tracker.db`.
+- Ink changes for each pen are recorded in `pen_ink_history`, including transitions to `N/A`.
+- When modifying storage columns, update both `engine.py` and `cli.py` to maintain field mappings and database behavior.
+- One-based IDs are used consistently for user-facing selection and display.
+- SQLite persistence always sorts data before saving.
+
+## Testing
+
+- `tests/test_engine.py` contains test coverage for the core engine layer.
+- Add tests for new fields, storage behavior, and CLI data validation if extending features.
+
+## Notes for AI agents
+
+- Focus on `src/pen_tracker/engine.py` for the data model and persistence logic.
+- Focus on `src/pen_tracker/cli.py` for user-facing behavior, commands, and interactive menu flow.
+- The default storage paths are derived from XDG conventions and environment variables.
+- There is no GUI, web service, or database; all data is stored in CSV files.
+- The project version is `0.5.0` and the package name is `pen-tracker`.
+
+## Extension suggestions
+
+- Add unit tests for the CLI parser and interactive menu flows.
+- Add a dedicated `docs/` folder if more formal design docs or API references are needed.
+- Add JSON schema validation or stronger date handling if data robustness is required.
diff --git a/README.md b/README.md
index ad359b5..92f7cbb 100644
--- a/README.md
+++ b/README.md
@@ -10,9 +10,9 @@ pip install .
 
 ## Data Storage
 
-Pen data is stored in `~/.local/share/pen-tracker/pens.csv` by default, following XDG Base Directory specification. The directory is created automatically if it doesn't exist.
+Data is stored in a SQLite database by default at `~/.local/share/pen-tracker/pen_tracker.db`, following the XDG Base Directory specification. The directory is created automatically if it doesn't exist.
 
-You can override the location by setting the `PEN_TRACKER_CSV` environment variable.
+You can override the location by setting the `PEN_TRACKER_DB` environment variable or using `--db` when running the CLI.
 
 ## Usage
 
@@ -25,11 +25,20 @@ pen-tracker
 
 Command-line mode:
 ```bash
-pen-tracker add --make "Pilot" --model "Metropolitan" --nib "F"
+pen-tracker --db ~/.local/share/pen-tracker/pen_tracker.db add --make "Pilot" --model "Metropolitan" --nib "F"
 pen-tracker list
 pen-tracker export --output my_pens.json
 ```
 
+### Import CSV data
+
+If you are migrating from the old CSV storage format, run:
+```bash
+python import_csv_to_sqlite.py --db ~/.local/share/pen-tracker/pen_tracker.db
+```
+
+The import script will initialize the SQLite database if it does not already exist.
+
 ## Features
 
 - Track fountain pens with details like make, model, nib, ink, etc.
diff --git a/__pycache__/import_csv_to_sqlite.cpython-313.pyc b/__pycache__/import_csv_to_sqlite.cpython-313.pyc
new file mode 100644
index 0000000..9a2f0de
Binary files /dev/null and b/__pycache__/import_csv_to_sqlite.cpython-313.pyc differ
diff --git a/import_csv_to_sqlite.py b/import_csv_to_sqlite.py
new file mode 100755
index 0000000..fb7f518
--- /dev/null
+++ b/import_csv_to_sqlite.py
@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+import argparse
+import csv
+import os
+import sys
+from typing import Dict, List
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'src'))
+
+from pen_tracker.engine import Ink, InkTracker, Pen, PenTracker
+
+
+def get_default_pens_csv() -> str:
+    env_path = os.getenv('PEN_TRACKER_CSV')
+    if env_path:
+        return env_path
+    data_home = os.getenv('XDG_DATA_HOME', os.path.expanduser('~/.local/share'))
+    app_data_dir = os.path.join(data_home, 'pen-tracker')
+    os.makedirs(app_data_dir, exist_ok=True)
+    return os.path.join(app_data_dir, 'pens.csv')
+
+
+def get_default_inks_csv() -> str:
+    env_path = os.getenv('INK_TRACKER_CSV')
+    if env_path:
+        return env_path
+    data_home = os.getenv('XDG_DATA_HOME', os.path.expanduser('~/.local/share'))
+    app_data_dir = os.path.join(data_home, 'pen-tracker')
+    os.makedirs(app_data_dir, exist_ok=True)
+    return os.path.join(app_data_dir, 'inks.csv')
+
+
+def load_csv_rows(path: str, fieldnames: List[str]) -> List[Dict[str, str]]:
+    if not os.path.exists(path):
+        return []
+
+    with open(path, mode='r', encoding='utf-8-sig', newline='') as f:
+        reader = csv.DictReader(f)
+        if reader.fieldnames:
+            reader.fieldnames = [h.strip() for h in reader.fieldnames]
+        rows: List[Dict[str, str]] = []
+        for row in reader:
+            clean_row = {k.strip(): (v.strip() if v else 'N/A') for k, v in row.items() if k is not None}
+            for field in fieldnames:
+                clean_row.setdefault(field, 'N/A')
+            rows.append(clean_row)
+    return rows
+
+
+def import_data(db_path: str, pens_csv: str, inks_csv: str) -> None:
+    ink_tracker = InkTracker(db_path)
+    pen_tracker = PenTracker(db_path)
+
+    ink_rows = load_csv_rows(inks_csv, ink_tracker.headers)
+    inks = [Ink(**row) for row in ink_rows]
+    ink_tracker.inks = inks
+    ink_tracker.save_data()
+
+    pen_rows = load_csv_rows(pens_csv, pen_tracker.headers)
+    pens = [Pen(**{pen_tracker.key_map.get(k, k): v for k, v in row.items()}) for row in pen_rows]
+    pen_tracker.pens = pens
+    pen_tracker.save_data()
+
+    print(f'Imported {len(ink_tracker.inks)} inks from {inks_csv}')
+    print(f'Imported {len(pen_tracker.pens)} pens from {pens_csv}')
+    print(f'SQLite database initialized at: {db_path}')
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description='Import CSV data into pen-tracker SQLite database')
+    parser.add_argument('--db', default=None, help='Path to the SQLite database file')
+    parser.add_argument('--pens-csv', default=None, help='Path to pens CSV file')
+    parser.add_argument('--inks-csv', default=None, help='Path to inks CSV file')
+    args = parser.parse_args()
+
+    db_path = args.db
+    pens_csv = args.pens_csv or get_default_pens_csv()
+    inks_csv = args.inks_csv or get_default_inks_csv()
+
+    import_data(db_path, pens_csv, inks_csv)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/pyproject.toml b/pyproject.toml
index b2763bb..24017fb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "pen-tracker"
-version = "0.5.0"
+version = "0.5.1"
 authors = [
   { name="Don Harper", email="don@donharper.org" },
 ]
diff --git a/src/pen_tracker.egg-info/PKG-INFO b/src/pen_tracker.egg-info/PKG-INFO
index 26d8654..57bafce 100644
--- a/src/pen_tracker.egg-info/PKG-INFO
+++ b/src/pen_tracker.egg-info/PKG-INFO
@@ -1,6 +1,6 @@
 Metadata-Version: 2.4
 Name: pen-tracker
-Version: 0.5.0
+Version: 0.5.1
 Summary: A fountain pen collection tracker.
 Author-email: Don Harper <don@donharper.org>
 Requires-Python: >=3.8
@@ -20,9 +20,9 @@ pip install .
 
 ## Data Storage
 
-Pen data is stored in `~/.local/share/pen-tracker/pens.csv` by default, following XDG Base Directory specification. The directory is created automatically if it doesn't exist.
+Data is stored in a SQLite database by default at `~/.local/share/pen-tracker/pen_tracker.db`, following the XDG Base Directory specification. The directory is created automatically if it doesn't exist.
 
-You can override the location by setting the `PEN_TRACKER_CSV` environment variable.
+You can override the location by setting the `PEN_TRACKER_DB` environment variable or using `--db` when running the CLI.
 
 ## Usage
 
@@ -35,11 +35,20 @@ pen-tracker
 
 Command-line mode:
 ```bash
-pen-tracker add --make "Pilot" --model "Metropolitan" --nib "F"
+pen-tracker --db ~/.local/share/pen-tracker/pen_tracker.db add --make "Pilot" --model "Metropolitan" --nib "F"
 pen-tracker list
 pen-tracker export --output my_pens.json
 ```
 
+### Import CSV data
+
+If you are migrating from the old CSV storage format, run:
+```bash
+python import_csv_to_sqlite.py --db ~/.local/share/pen-tracker/pen_tracker.db
+```
+
+The import script will initialize the SQLite database if it does not already exist.
+
 ## Features
 
 - Track fountain pens with details like make, model, nib, ink, etc.
diff --git a/src/pen_tracker/__pycache__/cli.cpython-313.pyc b/src/pen_tracker/__pycache__/cli.cpython-313.pyc
index 3860351..4fab421 100644
Binary files a/src/pen_tracker/__pycache__/cli.cpython-313.pyc and b/src/pen_tracker/__pycache__/cli.cpython-313.pyc differ
diff --git a/src/pen_tracker/__pycache__/engine.cpython-313.pyc b/src/pen_tracker/__pycache__/engine.cpython-313.pyc
index 507df11..4ff440f 100644
Binary files a/src/pen_tracker/__pycache__/engine.cpython-313.pyc and b/src/pen_tracker/__pycache__/engine.cpython-313.pyc differ
diff --git a/src/pen_tracker/cli.py b/src/pen_tracker/cli.py
index 9233355..a39b86b 100644
--- a/src/pen_tracker/cli.py
+++ b/src/pen_tracker/cli.py
@@ -1,5 +1,4 @@
 import os
-import csv
 import argparse
 import json
 from datetime import datetime
@@ -148,6 +147,23 @@ class CLITracker(PenTracker):
             field = self.key_map.get(header, header)
             value = getattr(pen, field)
             print(f"{header:<20}: {value}")
+
+        history = []
+        if pen.id is not None:
+            history = self.get_ink_history(pen.id)
+
+        print("═"*45)
+        print("\nInk Change History:")
+        if history:
+            print(f"{'When':<20} | {'Ink':<20}")
+            print("-" * 45)
+            for row in history:
+                changed_at = row.get('changed_at', 'N/A')
+                ink_name = row.get('ink_name', 'N/A')
+                print(f"{changed_at:<20} | {ink_name:<20}")
+        else:
+            print("No ink history available.")
+
         print("═"*45)
         input("\nPress Enter to return to menu...")
 
@@ -192,7 +208,7 @@ class CLITracker(PenTracker):
         new_ink = Ink(**new_ink_data)
         self.ink_tracker.inks.append(new_ink)
         self.ink_tracker.save_data()
-        print("\n[✔] Ink added successfully to inks.csv!")
+        print("\n[✔] Ink added successfully!")
 
     def view_all_inks(self):
         if not self.ink_tracker.inks:
@@ -237,7 +253,7 @@ def clear_screen():
 def main():
     # This is the entry point defined in pyproject.toml
     parser = argparse.ArgumentParser(description="Fountain Pen Tracker")
-    parser.add_argument('--csv', default=None, help='Path to CSV file')
+    parser.add_argument('--db', default=None, help='Path to SQLite database file')
     subparsers = parser.add_subparsers(dest='command', help='Commands')
 
     # Add command
@@ -275,7 +291,7 @@ def main():
 
     args = parser.parse_args()
 
-    tracker = CLITracker(args.csv)
+    tracker = CLITracker(args.db)
 
     if args.command == 'add':
         # Validate dates
@@ -331,7 +347,7 @@ def main():
     else:
         # Interactive mode
         while True:
-            print("\n🖋️  FOUNTAIN PEN TRACKER (CSV Edition)")
+            print("\n🖋️  FOUNTAIN PEN TRACKER (SQLite Edition)")
             print("1. View Collection Summary")
             print("2. Add New Pen")
             print("3. Edit a Pen")
diff --git a/src/pen_tracker/engine.py b/src/pen_tracker/engine.py
index d3117c2..7afe9e9 100644
--- a/src/pen_tracker/engine.py
+++ b/src/pen_tracker/engine.py
@@ -1,163 +1,278 @@
-import csv
 import os
+import sqlite3
 import logging
-from dataclasses import dataclass, asdict
-from typing import List
+from dataclasses import dataclass
+from typing import Any, Dict, List, Optional, Sequence, Set, Tuple
 
 logger = logging.getLogger(__name__)
 
+
+def get_default_db_path(db_path: Optional[str] = None) -> str:
+    if db_path:
+        return db_path
+    env_path = os.getenv('PEN_TRACKER_DB')
+    if env_path:
+        return env_path
+    data_home = os.getenv('XDG_DATA_HOME', os.path.expanduser('~/.local/share'))
+    app_data_dir = os.path.join(data_home, 'pen-tracker')
+    os.makedirs(app_data_dir, exist_ok=True)
+    return os.path.join(app_data_dir, 'pen_tracker.db')
+
+
+class SqliteStore:
+    def __init__(self, db_path: Optional[str] = None):
+        self.db_path = get_default_db_path(db_path)
+        self.conn = sqlite3.connect(self.db_path)
+        self.conn.row_factory = sqlite3.Row
+        self.conn.execute('PRAGMA foreign_keys = ON')
+        self.initialize_db()
+
+    def initialize_db(self):
+        self.conn.execute(
+            '''CREATE TABLE IF NOT EXISTS inks (
+                id INTEGER PRIMARY KEY,
+                vendor TEXT NOT NULL,
+                name TEXT NOT NULL,
+                color TEXT NOT NULL,
+                purchased TEXT NOT NULL,
+                size TEXT NOT NULL,
+                notes TEXT NOT NULL
+            )'''
+        )
+        self.conn.execute(
+            '''CREATE TABLE IF NOT EXISTS pens (
+                id INTEGER PRIMARY KEY,
+                make TEXT NOT NULL,
+                model TEXT NOT NULL,
+                date_purchased TEXT NOT NULL,
+                vendor TEXT NOT NULL,
+                nib TEXT NOT NULL,
+                nib_material TEXT NOT NULL,
+                body TEXT NOT NULL,
+                cap TEXT NOT NULL,
+                post TEXT NOT NULL,
+                current_ink TEXT NOT NULL,
+                inked_date TEXT NOT NULL,
+                notes TEXT NOT NULL
+            )'''
+        )
+        self.conn.execute(
+            '''CREATE TABLE IF NOT EXISTS pen_ink_history (
+                id INTEGER PRIMARY KEY,
+                pen_id INTEGER NOT NULL,
+                ink_name TEXT NOT NULL,
+                changed_at TEXT NOT NULL DEFAULT (datetime('now')),
+                FOREIGN KEY(pen_id) REFERENCES pens(id) ON DELETE CASCADE
+            )'''
+        )
+        self.conn.commit()
+
+    def execute(self, query: str, params: Tuple[Any, ...] = ()):
+        return self.conn.execute(query, params)
+
+    def executemany(self, query: str, seq_of_params: Sequence[Tuple[Any, ...]]):
+        return self.conn.executemany(query, seq_of_params)
+
+    def fetchall(self, query: str, params: Tuple[Any, ...] = ()) -> List[Dict[str, Any]]:
+        cursor = self.conn.execute(query, params)
+        return [dict(row) for row in cursor.fetchall()]
+
+    def commit(self):
+        self.conn.commit()
+
+    def close(self):
+        self.conn.close()
+
+
 @dataclass
 class Ink:
-    Vendor: str = "N/A"
-    Name: str = "N/A"
-    Color: str = "N/A"
-    Purchased: str = "N/A"
-    Size: str = "N/A"
-    Notes: str = "N/A"
+    Vendor: str = 'N/A'
+    Name: str = 'N/A'
+    Color: str = 'N/A'
+    Purchased: str = 'N/A'
+    Size: str = 'N/A'
+    Notes: str = 'N/A'
+    id: Optional[int] = None
+
 
 @dataclass
 class Pen:
-    Make: str = "N/A"
-    Model: str = "N/A"
-    Date_Purchased: str = "N/A"
-    Vendor: str = "N/A"
-    Nib: str = "N/A"
-    Nib_Material: str = "N/A"
-    Body: str = "N/A"
-    Cap: str = "N/A"
-    Post: str = "N/A"
-    Current_Ink: str = "N/A"
-    Inked_date: str = "N/A"
-    Notes: str = "N/A"
+    Make: str = 'N/A'
+    Model: str = 'N/A'
+    Date_Purchased: str = 'N/A'
+    Vendor: str = 'N/A'
+    Nib: str = 'N/A'
+    Nib_Material: str = 'N/A'
+    Body: str = 'N/A'
+    Cap: str = 'N/A'
+    Post: str = 'N/A'
+    Current_Ink: str = 'N/A'
+    Inked_date: str = 'N/A'
+    Notes: str = 'N/A'
+    id: Optional[int] = None
+
 
 class InkTracker:
-    def __init__(self, storage_file: str = None):
-        if storage_file is None:
-            storage_file = os.getenv('INK_TRACKER_CSV')
-            if storage_file is None:
-                data_home = os.getenv('XDG_DATA_HOME', os.path.expanduser('~/.local/share'))
-                app_data_dir = os.path.join(data_home, 'pen-tracker')
-                os.makedirs(app_data_dir, exist_ok=True)
-                storage_file = os.path.join(app_data_dir, 'inks.csv')
-        self.storage_file = storage_file
+    def __init__(self, db_path: Optional[str] = None):
+        self.db = SqliteStore(db_path)
         self.headers = ['Vendor', 'Name', 'Color', 'Purchased', 'Size', 'Notes']
         self.inks: List[Ink] = self.load_data()
 
     def _sort_inks(self):
-        """Sorts the inks list by Vendor, then by Name alphabetically."""
         self.inks.sort(key=lambda x: (x.Vendor.lower(), x.Name.lower()))
 
     def load_data(self) -> List[Ink]:
-        """Loads data from the CSV file."""
-        if not os.path.exists(self.storage_file):
-            self._create_empty_csv()
-            return []
-        
-        inks = []
-        try:
-            with open(self.storage_file, mode='r', encoding='utf-8-sig') as f:
-                reader = csv.DictReader(f)
-                if reader.fieldnames:
-                    reader.fieldnames = [h.strip() for h in reader.fieldnames]
-                for row in reader:
-                    if None in row:
-                        extras = row.pop(None)
-                        if extras:
-                            extra_text = ",".join(extras).strip()
-                            if extra_text:
-                                row['Notes'] = (row.get('Notes') or '')
-                                if row['Notes']:
-                                    row['Notes'] += ", "
-                                row['Notes'] += extra_text
-                    clean_row = {
-                        k.strip(): (v.strip() if v else "N/A")
-                        for k, v in row.items() if k is not None
-                    }
-                    inks.append(Ink(**clean_row))
-            inks.sort(key=lambda x: (x.Vendor.lower(), x.Name.lower()))
-        except Exception as e:
-            logger.error(f"Error loading inks CSV: {e}")
+        rows = self.db.fetchall(
+            'SELECT * FROM inks ORDER BY vendor COLLATE NOCASE, name COLLATE NOCASE'
+        )
+        inks: List[Ink] = []
+        for row in rows:
+            inks.append(
+                Ink(
+                    Vendor=row['vendor'],
+                    Name=row['name'],
+                    Color=row['color'],
+                    Purchased=row['purchased'],
+                    Size=row['size'],
+                    Notes=row['notes'],
+                    id=row['id'],
+                )
+            )
         return inks
 
-    def _create_empty_csv(self):
-        """Creates the CSV file with headers if it is missing."""
-        with open(self.storage_file, mode='w', newline='', encoding='utf-8') as f:
-            writer = csv.DictWriter(f, fieldnames=self.headers)
-            writer.writeheader()
-
     def save_data(self):
-        """Sorts the data before writing to ensure persistent alphabetical order."""
         self._sort_inks()
-        with open(self.storage_file, mode='w', newline='', encoding='utf-8') as f:
-            writer = csv.DictWriter(f, fieldnames=self.headers)
-            writer.writeheader()
-            for ink in self.inks:
-                writer.writerow(asdict(ink))
+        self.db.execute('DELETE FROM inks')
+        for ink in self.inks:
+            cursor = self.db.execute(
+                'INSERT INTO inks (vendor, name, color, purchased, size, notes) VALUES (?, ?, ?, ?, ?, ?)',
+                (ink.Vendor, ink.Name, ink.Color, ink.Purchased, ink.Size, ink.Notes),
+            )
+            ink.id = cursor.lastrowid
+        self.db.commit()
+        self.inks = self.load_data()
+
 
 class PenTracker:
-    def __init__(self, storage_file: str = None):
-        if storage_file is None:
-            storage_file = os.getenv('PEN_TRACKER_CSV')
-            if storage_file is None:
-                data_home = os.getenv('XDG_DATA_HOME', os.path.expanduser('~/.local/share'))
-                app_data_dir = os.path.join(data_home, 'pen-tracker')
-                os.makedirs(app_data_dir, exist_ok=True)
-                storage_file = os.path.join(app_data_dir, 'pens.csv')
-        self.storage_file = storage_file
+    def __init__(self, db_path: Optional[str] = None):
+        self.db = SqliteStore(db_path)
         self.headers = [
             'Make', 'Model', 'Date-Purchased', 'Vendor', 'Nib',
             'Nib-Material', 'Body', 'Cap', 'Post',
-            'Current-Ink', 'Inked-date', 'Notes'
+            'Current-Ink', 'Inked-date', 'Notes',
         ]
         self.key_map = {
             'Date-Purchased': 'Date_Purchased',
             'Inked-date': 'Inked_date',
             'Nib-Material': 'Nib_Material',
-            'Current-Ink': 'Current_Ink'
+            'Current-Ink': 'Current_Ink',
         }
         self.reverse_key_map = {v: k for k, v in self.key_map.items()}
         self.pens: List[Pen] = self.load_data()
 
     def _sort_pens(self):
-        """Sorts the pens list by Make, then by Model alphabetically."""
         self.pens.sort(key=lambda x: (x.Make.lower(), x.Model.lower()))
 
     def load_data(self) -> List[Pen]:
-        """Loads data from the CSV file."""
-        if not os.path.exists(self.storage_file):
-            self._create_empty_csv()
-            return []
-        
-        pens = []
-        try:
-            # Standard, clean way to open the file
-            with open(self.storage_file, mode='r', encoding='utf-8-sig') as f:
-                reader = csv.DictReader(f)
-                for row in reader:
-                    # Strip whitespace from keys and values, handle empty values
-                    clean_row = {k.strip(): (v.strip() if v else "N/A") for k, v in row.items()}
-                    # Map keys to dataclass field names
-                    mapped_row = {self.key_map.get(k, k): v for k, v in clean_row.items()}
-                    pens.append(Pen(**mapped_row))
-            pens.sort(key=lambda x: (x.Make.lower(), x.Model.lower()))
-        except Exception as e:
-            logger.error(f"Error loading CSV: {e}")
+        rows = self.db.fetchall(
+            'SELECT * FROM pens ORDER BY make COLLATE NOCASE, model COLLATE NOCASE'
+        )
+        pens: List[Pen] = []
+        for row in rows:
+            pens.append(
+                Pen(
+                    Make=row['make'],
+                    Model=row['model'],
+                    Date_Purchased=row['date_purchased'],
+                    Vendor=row['vendor'],
+                    Nib=row['nib'],
+                    Nib_Material=row['nib_material'],
+                    Body=row['body'],
+                    Cap=row['cap'],
+                    Post=row['post'],
+                    Current_Ink=row['current_ink'],
+                    Inked_date=row['inked_date'],
+                    Notes=row['notes'],
+                    id=row['id'],
+                )
+            )
         return pens
 
-    def _create_empty_csv(self):
-        """Creates the CSV file with headers if it is missing."""
-        with open(self.storage_file, mode='w', newline='', encoding='utf-8') as f:
-            writer = csv.DictWriter(f, fieldnames=self.headers)
-            writer.writeheader()
+    def _insert_pen(self, pen: Pen) -> int:
+        cursor = self.db.execute(
+            'INSERT INTO pens (make, model, date_purchased, vendor, nib, nib_material, body, cap, post, current_ink, inked_date, notes) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)',
+            (
+                pen.Make,
+                pen.Model,
+                pen.Date_Purchased,
+                pen.Vendor,
+                pen.Nib,
+                pen.Nib_Material,
+                pen.Body,
+                pen.Cap,
+                pen.Post,
+                pen.Current_Ink,
+                pen.Inked_date,
+                pen.Notes,
+            ),
+        )
+        row_id = cursor.lastrowid
+        return int(row_id) if row_id is not None else 0
+
+    def _update_pen(self, pen: Pen):
+        self.db.execute(
+            'UPDATE pens SET make = ?, model = ?, date_purchased = ?, vendor = ?, nib = ?, nib_material = ?, body = ?, cap = ?, post = ?, current_ink = ?, inked_date = ?, notes = ? WHERE id = ?',
+            (
+                pen.Make,
+                pen.Model,
+                pen.Date_Purchased,
+                pen.Vendor,
+                pen.Nib,
+                pen.Nib_Material,
+                pen.Body,
+                pen.Cap,
+                pen.Post,
+                pen.Current_Ink,
+                pen.Inked_date,
+                pen.Notes,
+                pen.id,
+            ),
+        )
+
+    def _record_history(self, pen_id: int, ink_name: str):
+        self.db.execute(
+            'INSERT INTO pen_ink_history (pen_id, ink_name) VALUES (?, ?)',
+            (pen_id, ink_name),
+        )
+
+    def get_ink_history(self, pen_id: int) -> List[Dict[str, str]]:
+        return self.db.fetchall(
+            'SELECT * FROM pen_ink_history WHERE pen_id = ? ORDER BY changed_at',
+            (pen_id,),
+        )
 
     def save_data(self):
-        """Sorts the data before writing to ensure persistent alphabetical order."""
         self._sort_pens()
-        with open(self.storage_file, mode='w', newline='', encoding='utf-8') as f:
-            writer = csv.DictWriter(f, fieldnames=self.headers)
-            writer.writeheader()
-            for pen in self.pens:
-                row = asdict(pen)
-                # Map back to CSV keys
-                csv_row = {k.replace('_', '-'): v for k, v in row.items()}
-                writer.writerow(csv_row)
+        existing_rows = {row['id']: row for row in self.db.fetchall('SELECT * FROM pens')}
+        seen_ids: Set[int] = set()
+
+        for pen in self.pens:
+            if pen.id is None:
+                pen.id = self._insert_pen(pen)
+                self._record_history(pen.id, pen.Current_Ink)
+            else:
+                old_row = existing_rows.pop(pen.id, None)
+                if old_row is None:
+                    pen.id = self._insert_pen(pen)
+                    self._record_history(pen.id, pen.Current_Ink)
+                else:
+                    if old_row['current_ink'] != pen.Current_Ink:
+                        self._record_history(pen.id, pen.Current_Ink)
+                    self._update_pen(pen)
+            seen_ids.add(pen.id)
+
+        for orphan_id in existing_rows.keys():
+            self.db.execute('DELETE FROM pens WHERE id = ?', (orphan_id,))
+
+        self.db.commit()
+        self.pens = self.load_data()
diff --git a/tests/__pycache__/test_engine.cpython-313.pyc b/tests/__pycache__/test_engine.cpython-313.pyc
index 69504fe..1af50c5 100644
Binary files a/tests/__pycache__/test_engine.cpython-313.pyc and b/tests/__pycache__/test_engine.cpython-313.pyc differ
diff --git a/tests/test_engine.py b/tests/test_engine.py
index dfdce76..88e0b13 100644
--- a/tests/test_engine.py
+++ b/tests/test_engine.py
@@ -1,11 +1,11 @@
-import unittest
-import tempfile
 import os
-from pen_tracker.engine import PenTracker, Pen, InkTracker, Ink
+import tempfile
+import unittest
+from pen_tracker.engine import Ink, InkTracker, Pen, PenTracker
 
 class TestPenTracker(unittest.TestCase):
     def setUp(self):
-        self.temp_file = tempfile.NamedTemporaryFile(delete=False, suffix='.csv')
+        self.temp_file = tempfile.NamedTemporaryFile(delete=False, suffix='.db')
         self.temp_file.close()
         self.tracker = PenTracker(self.temp_file.name)
 
@@ -33,11 +33,28 @@ class TestPenTracker(unittest.TestCase):
         self.assertEqual(new_tracker.pens[0].Make, "A")
         self.assertEqual(new_tracker.pens[1].Make, "Z")
 
+    def test_pen_ink_history_records_changes(self):
+        pen = Pen(Make="Pilot", Model="Metropolitan", Nib="F", Current_Ink="Blue")
+        self.tracker.pens.append(pen)
+        self.tracker.save_data()
+
+        persisted = self.tracker.pens[0]
+        history = self.tracker.get_ink_history(persisted.id)
+        self.assertEqual(len(history), 1)
+        self.assertEqual(history[0]['ink_name'], "Blue")
+
+        persisted.Current_Ink = "N/A"
+        self.tracker.save_data()
+
+        history = self.tracker.get_ink_history(persisted.id)
+        self.assertEqual(len(history), 2)
+        self.assertEqual(history[-1]['ink_name'], "N/A")
+
 
 
 class TestInkTracker(unittest.TestCase):
     def setUp(self):
-        self.temp_file = tempfile.NamedTemporaryFile(delete=False, suffix='.csv')
+        self.temp_file = tempfile.NamedTemporaryFile(delete=False, suffix='.db')
         self.temp_file.close()
         self.tracker = InkTracker(self.temp_file.name)
 
@@ -64,20 +81,14 @@ class TestInkTracker(unittest.TestCase):
         self.assertEqual(new_tracker.inks[0].Vendor, "A")
         self.assertEqual(new_tracker.inks[1].Vendor, "Z")
 
-    def test_loads_row_with_extra_trailing_field(self):
-        csv_content = (
-            "Vendor,Name,Color,Purchased,Size,Notes\n"
-            "Waterman,Intense Black,Black,,\"Cartridge,International Short\",\n"
-            "Pilot,Black Cartridge,Black,2024-01-01,Cartridge,Good ink\n"
-        )
-        with open(self.temp_file.name, 'w', encoding='utf-8') as f:
-            f.write(csv_content)
+    def test_save_and_load_ink(self):
+        self.tracker.inks.append(Ink(Vendor='Waterman', Name='Intense Black', Color='Black', Notes='Good ink'))
+        self.tracker.save_data()
 
         new_tracker = InkTracker(self.temp_file.name)
-        self.assertEqual(len(new_tracker.inks), 2)
-        self.assertEqual(new_tracker.inks[0].Vendor, "Pilot")
-        self.assertEqual(new_tracker.inks[1].Vendor, "Waterman")
-        self.assertEqual(new_tracker.inks[1].Notes, "N/A")
+        self.assertEqual(len(new_tracker.inks), 1)
+        self.assertEqual(new_tracker.inks[0].Vendor, 'Waterman')
+        self.assertEqual(new_tracker.inks[0].Name, 'Intense Black')
 
 if __name__ == '__main__':
     unittest.main()
\ No newline at end of file