One of the hallmarks of the Planar Cell Polarity pathway is the asymmetric distribution of proteins on opposite membranes of a single cell. In Drosophila, Stbm and Pk (homologues to the human VANGL1/2 and PRICKLE1/2/3) colocalize opposite Fz, Dsh and Dgo (FZD, DVL, and ANKRD6, respectively). The two complexes antagonize each other, with Fz:Dsh:Dgo acting to promote signaling downstream of Dsh, while the Stbm:Pk complex restricts this signaling (reviewed in Seifert and Mlodzik, 2007). Asymmetric localization of some PCP proteins is also seen in vertebrates (Montcouquiol et al, 2003, 2006; Wang et al, 2006, Narimatsu et al, 2009) although the patterns of localization differ from that of flies. The details of how localization is established and how the asymmetrical distribution of proteins is translated into gross morphological processes remain to be fully elucidated.