The outer root sheath (ORS) of the hair follicle surrounds the hair fiber and inner root sheath. It cames from the epidermis by downward growth. The ORS consists of basal, prickle cells and granular layers near the opening of the follicle onto the skin surface, and modified glycogen-rich prickle cells in the deeper parts of the follicle. The ORS contains several cell populations which play a role in certain functions of the hair follicle; such as serving as a sensory organ and an immunologic sentinel of the skin. The ORS contains nestin-expressing stem cells, with a variable location of the nestin-expressing stem cells based on the hair cycle. Human Hair Outer Root Sheath Cells further represents an alternate source of keratinocytes, which are suitable for skin replacement.