Circle packing can be a useful way to visualize hierarchical data, as demonstrated here with a visualization of the class hierarchy of the GoJS library. This layout is performed automatically by the PackedLayout extension. Nodes are sized according to how many properties their corresponding class has, or has inherited. As a result, larger nodes generally represent more complex classes. Mouse over nodes to see their full name and the number of properties on their corresponding class.
This sample is very similar to the Class Hierarchy sample, except that instead of showing the class hierarchy as a tree, it is displayed using nested circles. Opening the API page is achieved by double-clicking on a node, rather than using a "HyperlinkText".