Treemaps support visualization of large hierarchical information spaces. The treemap generation algorithm is straightforward and application prototypes have only minimal hardware requirements. Given primary graphical encodings of area, color and enclosure, treemaps are best suited for the tasks of outlier detection, cause-effect analysis and location of specific nodes--satisfying user-specified criteria--in their hierarchical context. Distortion effects extend treemap capabilities by emphasizing node relationships in the diagram.