Enclosure diagrams are data visualization aids that use filled spaces (usually rectangles) that are contained within larger rectangles to designate the relative size of each data set and subset. In the popular treemap version of the enclosure diagram, clusters of related nodes of varying sizes are enclosed together as nesting rectangles configured to represent branches and leaves. Subsets and sub-subsets of data in the hierarchy are represented by smaller and smaller rectangles within each enclosure. A treemap uses a tiling algorithm to maintain an aspect ratio and rectangle placement that is easy to grasp visually.Enclosure diagrams are used to reveal the hierarchical relationship between different elements of data. They are particularly useful for revealing the dimensional relationship of data. For example, an enclosure diagram might indicate the relative dollar value of various exports or national spending across a variety of categories (e.g., military vs. international aid). Treemaps can represent a great deal of data in a small display area because of the nested nature of the diagram. Enclosure diagrams may be structured using other shapes such as circles when screen space is less limited. Colors can be used in addition to size to indicate additional aspects of each data set. This color coding may reveal new information such as the prevalence of a certain dimension of the data that is not revealed by size or placement in the hierarchy.