Developmental origins of dermal papilla cells - The precursor of the hair follicle is a local thickening, also known as placode, of the embryonic epidermis, which is detectable at embryonic day 14.5 (E14.5) of mouse development. Soon after, a local condensation (dermal condensate) of fibroblasts forms beneath the placode. Reciprocal signalling between the condensate and the placode leads to proliferation of the overlying epithelium and downward extension of the new follicle into the dermis (Millar, 2002; Schneider et al., 2009; Ohyama et al., 2010; Yang and Cotsarelis, 2010). After the initial downward growth, the epithelial cells envelope the dermal condensate, thereby forming the mature DP. The DP then instructs the surrounding epithelial cells, now called matrix cells, to proliferate, move upward and differentiate into the multiple layers of the outgrowing hair shaft and the channel surrounding the hair shaft, called the inner root sheath (Millar, 2002; Schneider et al., 2009).