Wendell A. Lim is Professor of Cellular and Molecular Pharmacology at the University of California, San Francisco. The principal focus of his research is the structure and mechanism of protein interaction domains and the logic by which these components are used to build complex cellular signaling systems. Bruce J. Mayer is Professor of Genetics and Genome Sciences at the University of Connecticut, School of Medicine. Current work of his group focuses on characterizing and manipulating tyrosine kinase–mediated signal transduction pathways.