trees show hierarchical data. File directory navigation is one of the most familiar UX for browsing a tree.
There are numerous variations on presentation of a tree:
(above examples from Protovis library)
Here's a more complete visual gallery of some of the methods.
- Some variations for deep hierarchies.
- Dealing with a tree with 100,000's of nodes in an industrial controller context.
- Comparison of Miller columns and conventional trees.
Creating a 'tree' question
Try to get whatever is special about your tree question into the question title. We've already had questions about large trees and deep trees and about what the options are. If it's not clear your question is different you'll get pointed to those.