Stratum germinativum (also stratum basale or basal cell layer) is the layer of keratinocytes that lies at the base of the epiermis immediately above the dermis. It consists of a single layer of tall, simple columnar epithelial cells lying on a basement membrane. These cells undergo rapid cell division, mitosis, to replenish the regular loss of skin by shedding from the surface. About 25% of the cells are melanocytes, which produce melanin, which provides pigmentation for skin and hair.