the book "Pro WPF in c# 2008" show a diagram with the class hierarchy of the fundamental classes of WPF. these are the classes:
->DispatcherObject
^->DependencyObject
^->Visual
^->UIElement
^->FrameworkElement
Shape<-^->Control^->Panel
ContentControl<-^->ItemsControl
-System.Threading.DispatcherObject: WPF applications use the familiar single-thread affinity (STA) model, which means the entire user interface is owned by a single thread.
-System.Windows.DependencyObject: In WPF, the central way of interacting with onscreen elements is through properties.
-System.Windows.Media.Visual: Every element that appears in a WPF is, at heart, a Visual. You can think of the Visual class as a single drawing object, which encapsulates drawing instructions, additional details about how the drawing should be performed (such as clipping, opacity, and transformation settings), and basic functionality (such as hit testing).
-System.Windows.UIElement:UIElement adds support for WPF essentials such as layout, input, focus, and events (which the WPF team refers to by the acronym LIFE).
-System.Windows.FrameworkElement: FrameworkElement is the final stop in the core WPF inheritance tree. It implements some of the members that are merely defined by UIElement.
-System.Windows.Shapes.Shape: Basic shapes classes, such as Rectangle, Polygon, Ellipse, Line, and Path, derive from this class.
-System.Windows.Controls.Control: A control is an element that can interact with the user. It obviously includes classes such as TextBox, Button, and ListBox.
-System.Windows.Controls.ContentControl: This is the base class for all controls that have a single piece of content. This includes everything from the humble Label to the Window.
-System.Windows.Controls.ItemsControl: This is the base class for all controls that show a collection of items, such as the ListBox and TreeView.
-System.Windows.Controls.Panel: This is the base class for all layout containers—elements that can contain one or more children and arrange them according to specific layout rules.