Evolutionary trees, or phylogenies, are an essential tool in biology, used in all kinds of processes such as understanding evolution, designing new drugs, predicting gene expression, and determining the origin of a virus strain. Often, for one reason or another, scientists get a large set of possible phylogenies, and they would like to understand the structure of the set and the relationships between the various possible evolutionary trees. The Tree Set Visualization Project develops tools for efficiently understanding many possible phylogenies with interactive software.