Skin morphology is determined by an intricate array of developmental cues that act to induce the formation of skin adnexa (hair follicles), while development and maturation of the interfollicular epidermis is thought to occur as a default pathway (Kopan and Fuchs, 1989). Over the past several years, elegant investigations have been published describing the molecular regulation of hair follicle morphogenesis (reviewed in Oro and Scott, 1998; Schmidt-Ullrich and Paus, 2005). Here we will focus on molecular events involved in the development of the interfollicular epidermis. The majority of investigations on the molecular control of epidermal development cited in this review were performed using mouse models. This is because the technology to create knockout and transgenic mice provides outstanding tools for studying the coordinate control of epithelial cell growth and differentiation during development. However, for the most part, similar mechanisms also function