Treemap allows users to visualize data from an entire DNA microarray experiment in the context of the GO hierarchy on a single screen, and to access details about any gene on demand. (A) The Treemap data display and query window on the left uses area to convey quantitative information. A larger number of gene nodes exist in the biological process category of the GO (red circle), and that less area and fewer gene nodes exist in the molecular function (red circle), cellular component (red circle), and unlisted term (annotated genes without GO assignments) (red circle) categories. Selection of the entire Gene Ontology highlights this boxed area in yellow, and displays detailed information about the selected area in the "Details of selected node" window at the top right (red box). (B) Treemap allows access to data details without leaving the overview of the data. Selection of a single gene node box enables the user to see that the gene encoding Myb is transcribed in dying salivary glands (red circle), and the "Details of selected node" provides immediate quantitative and qualitative information about Myb in this experiment (red box).