Members of the protein kinase C (PKC) family are essential components of numerous signal transduction pathways and control a wide variety cellular processes. They form three subfamilies - the conventional, novel and atypical PKCs - and appear to have distinct but overlapping roles. In Cell Science at a Glance (see p. 131 + poster), Peter Parker and Judith Murray-Rust survey the various members of the PKC family, showing their phylogenetic relationships, their domain structures and the phenotypes of the various knockouts. An interactive version online contains PMID links for each knockout and 3D models of each domain.