The mechanisms of planar cell polarity, growth and the Hippo pathway: Some known unknowns

► We review the number of genetic pathways involved in PCP. ► The causal relationship between embryonic axes, morphogen gradients and PCP. ► The asymmetric localization of proteins involved in PCP. ► The roles of the Wnt genes in PCP in both vertebrates and Drosophila. ► The function of the Hippo pathway and its link to Fat.