The use of directed cell models to study the manner in which two or more cells interact has revolutionized our understanding of protein-protein interactions in a complex milieu and has provided an invaluable platform for the identification of new molecules. In Cell-Cell Interactions: Methods and Protocols, highly skilled experts in the development and utilization of cell-cell interaction assays describe in detail their best methods-based approaches, both in vitro and in vivo, for uncovering cellular interactions at the molecular level. The protocols cover a diverse set of cell-cell interaction models in both normal and pathological states, are readily adaptable to nearly any cell type and organ system, and include primary data and outcome analysis. In addition, the protocols follow the successful Methods in Molecular Biology series format, each offering step-by-step laboratory instructions, an introduction outlining the principles behind the technique, lists of the necessary equipment and reagents, and tips on troubleshooting and avoiding known pitfalls. Insightful to beginners and inspiring to seasoned professionals, Cell-Cell Interactions: Methods and Protocols provides the cutting-edge and versatile laboratory tools needed to gain a basic understanding of cell-cell interactions.