The Bin widget is a container with just one child. It is not very useful itself, but it is useful for deriving subclasses, since it provides common code needed for handling a single child widget.

Many Gtk+ widgets are subclasses of Bin, including Window, Button, Frame, HandleBox, and ScrolledWindow.

 |  GObject
 |   +----Object
 |         +----Widget
 |               +----Container
 |                     +----Bin
 |                           +----Window
 |                           +----Alignment
 |                           +----Frame
 |                           +----Button
 |                           +----Item
 |                           +----ComboBox
 |                           +----EventBox
 |                           +----Expander
 |                           +----HandleBox
 |                           +----ToolItem
 |                           +----ScrolledWindow
 |                           +----Viewport