A Hypothetical Protein Interaction Network. (a) A hypothetical protein interaction network. (b) A list of all maximal cliques in the network. (c) A naive representation of overlaps between maximal cliques. Each maximal clique is a node and there is an edge between two maximal cliques if and only if they share a protein. (d) The clique tree representation. Once again, every maximal clique is a node, but the cliques are connected in such a way that the resulting graph is a tree. Moreover, cliques that contain a given protein form a connected subgraph. (e) This color scheme is used to show the subtree of every protein. For example, protein 3 is contained in maximal cliques A, B, and C, which is shown by placing yellow dots above the maximal cliques.