diff --git a/Documentation.md b/Documentation.md
index 8e3f627..dd867cd 100644
--- a/Documentation.md
+++ b/Documentation.md
@@ -4,9 +4,9 @@
 1. [Overview](#overview)
 2. [Features](#features)
 3. [Code Structure](#code-structure)
-4. [Key Components](#key-components)
-5. [Data Flow](#data-flow)
-6. [API Reference](#api-reference)
+4. [Class Reference](#class-reference)
+5. [Function Documentation](#function-documentation)
+6. [Data Flow](#data-flow)
 7. [Usage Examples](#usage-examples)
 8. [Troubleshooting](#troubleshooting)
 
@@ -32,6 +32,7 @@ PNG Metadata Editor is a graphical application built with Python and Tkinter tha
 
 ```
 png-meta-editor.py
+├── Constants (APP_VERSION, APP_NAME)
 ├── PNGMetadataEditor (Main Class)
 │   ├── __init__() - Initialization
 │   ├── setup_ui() - UI Construction
@@ -44,61 +45,34 @@ png-meta-editor.py
     └── mark_as_modified()
 ```
 
-## Key Components
+## Class Reference
+
+### PNGMetadataEditor Class
 
-### Main Application Class
 ```python
 class PNGMetadataEditor:
     def __init__(self, root):
         # Initialize application state
-        self.current_file = None
-        self.metadata_dict = {}
-        self.has_unsaved_changes = False
+        self.current_file = None  # Currently loaded PNG file path
+        self.metadata_dict = {}   # Dictionary storing all metadata fields
+        self.has_unsaved_changes = False  # Track unsaved modifications
+        self.status_timer = None  # Timer for status messages
 ```
 
-### UI Components
-- **Treeview**: Displays metadata keys with truncated values
-- **Detail Text**: Shows full value of selected metadata
-- **Status Bar**: Provides feedback messages
-- **Dialogs**: Modal windows for adding/editing fields
-
-### Data Handling
-```python
-def open_file(self):
-    """Load PNG file and extract metadata"""
-    img = Image.open(filepath)
-    self.metadata_dict = dict(img.text)  # Extract all text chunks
-```
-
-## Data Flow
-
-1. **File Opening**:
-   - User selects PNG file → `open_file()` called
-   - PIL extracts text chunks → stored in `metadata_dict`
-   - UI refreshed with new data
-
-2. **Editing Process**:
-   - User selects field → `on_selection_change()` updates detail view
-   - Edit initiated → `edit_entry()` opens dialog
-   - Changes saved → `mark_as_modified()` updates state
-
-3. **Saving**:
-   - User clicks Save → `save_changes()` called
-   - New PngInfo object created with updated metadata
-   - File saved with `img.save()` using new metadata
-
-## API Reference
-
 ### Public Methods
+
 | Method | Description |
 |--------|-------------|
 | `open_file()` | Loads PNG file and extracts metadata |
 | `save_changes()` | Saves current metadata to file |
 | `add_field()` | Opens dialog to add new metadata field |
-| `edit_entry()` | Opens dialog to edit selected field |
+| `edit_entry(event=None)` | Opens dialog to edit selected field |
 | `delete_field()` | Removes selected metadata field |
+| `copy_value()` | Copies selected metadata value to clipboard |
+| `show_about()` | Displays application about dialog |
 
 ### Helper Methods
+
 ```python
 def format_value_for_display(self, value):
     """Try to parse as JSON for pretty printing"""
@@ -110,8 +84,113 @@ def format_value_for_display(self, value):
 def truncate_value(self, value, max_length=80):
     """Shorten long values for tree display"""
     return str(value)[:max_length] + "..." if len(str(value)) > max_length else str(value)
+
+def mark_as_modified(self):
+    """Mark the document as having unsaved changes"""
+    if not self.has_unsaved_changes:
+        self.has_unsaved_changes = True
+        self.update_title()
+        self.changes_label.config(text="Unsaved changes")
 ```
 
+## Function Documentation
+
+### Core Functions
+
+1. **`open_file()`**
+   - Opens a file dialog to select PNG file
+   - Extracts text chunks using PIL's `Image.text` attribute
+   - Populates `metadata_dict` with key-value pairs
+   - Refreshes UI to display new metadata
+
+2. **`save_changes()`**
+   - Creates new `PngInfo` object with current metadata
+   - Saves image with updated metadata using PIL's `img.save()`
+   - Marks changes as saved and updates UI state
+
+3. **`refresh_tree()`**
+   - Clears existing tree view items
+   - Repopulates with current metadata from `metadata_dict`
+   - Truncates long values for display in tree
+
+4. **`on_selection_change(event)`**
+   - Updates detail view when selection changes
+   - Formats selected value for display (JSON pretty-printing)
+   - Handles both JSON and plain text values
+
+### UI Management Functions
+
+1. **`set_status(message, duration=3000, color="")`**
+   - Displays temporary message in status bar
+   - Automatically clears after specified duration (ms)
+   - Supports colored messages for different status types
+
+2. **`update_title()`**
+   - Updates window title based on current state
+   - Shows filename when file is loaded
+   - Adds asterisk (*) for unsaved changes
+
+3. **`show_about()`**
+   - Displays application information dialog
+   - Shows version, description, author, and license
+   - Uses `messagebox.showinfo()` for standard dialog
+
+### Data Handling Functions
+
+1. **`format_value_for_display(value)`**
+   - Attempts to parse value as JSON
+   - Returns pretty-printed JSON if successful
+   - Falls back to string representation otherwise
+
+2. **`truncate_value(value, max_length=80)`**
+   - Shortens long values for tree display
+   - Adds ellipsis (...) to truncated values
+   - Preserves full value in detail view
+
+3. **`mark_as_modified()`**
+   - Sets unsaved changes flag
+   - Updates UI indicators (title, label)
+   - Prevents duplicate change notifications
+
+## Data Flow
+
+1. **File Opening**:
+   ```mermaid
+   sequenceDiagram
+     User->>App: Click "Open PNG File"
+     App->>FileDialog: Show open dialog
+     User->>App: Select PNG file
+     App->>PIL: Image.open(filepath)
+     PIL->>App: Extract text chunks
+     App->>metadata_dict: Store key-value pairs
+     App->>UI: Refresh tree and detail view
+   ```
+
+2. **Editing Process**:
+   ```mermaid
+   sequenceDiagram
+     User->>App: Select field in tree
+     App->>on_selection_change: Update detail view
+     User->>App: Click "Edit Field"
+     App->>Dialog: Show edit dialog
+     User->>App: Modify value
+     User->>App: Click "Save"
+     App->>metadata_dict: Update value
+     App->>mark_as_modified: Set unsaved flag
+     App->>UI: Refresh tree view
+   ```
+
+3. **Saving**:
+   ```mermaid
+   sequenceDiagram
+     User->>App: Click "Save Changes"
+     App->>PIL: Image.open(current_file)
+     App->>PngInfo: Create new metadata object
+     App->>PIL: img.save(pnginfo=metadata)
+     App->>mark_as_saved: Clear unsaved flag
+     App->>UI: Update status and title
+   ```
+
 ## Usage Examples
 
 ### Basic Workflow
@@ -120,13 +199,13 @@ def truncate_value(self, value, max_length=80):
 root = tk.Tk()
 app = PNGMetadataEditor(root)
 
-# Open a file (simulated)
+# Open a file programmatically (simulated)
 app.current_file = "example.png"
 img = Image.open("example.png")
 app.metadata_dict = dict(img.text)
 app.refresh_tree()
 
-# Edit a field
+# Edit a field programmatically
 app.edit_entry()  # Would normally be triggered by UI event
 
 # Save changes