[noun] The skin is a living organ and its cells have their own natural life cycle. Cellular renewal is the process of shedding dead cells and creating new ones. “Young” cells, or keratinocytes, are produced in the basal layer at the base of the epidermis. Then, as the days pass, the cells rise to the skin’s surface and turn into dead cells. This means that the epidermis is naturally renewed in a period of 21 to 28 days.