Stem cells are unspecialized cells that have two defining properties: the ability to differentiate into other cells and the ability to self-regenerate. Although it has been known for decades that epithelial stem cells can be identified as label-retaining cells (LRCs) by long term retention of a nuclear label, isolating a pure population of stem cells has been problematic. Epidermal stem cells reside in both rete ridges and over dermal papilla and do not appear to be clustered at any specific location in the basal compartment.Epidermal stem cells are important because they not only play a central role in homeostasis and wound repair, but also represent a major target of tumor initiation and gene therapy. Stem cells have been used in trials for treating several dermatologic and non-dermatologic conditions.