Your skin is composed of several layers. The layer you can see is called the epidermis. It is composed of cells made of keratin, a hard substance that also forms your hair and nails. The individual cells are called keratinocytes. New keratinocytes grow at the lowest level of the epidermis, which bonds with the next layer, the dermis. The new skin cells gradually push their way to the top layer. When they reach the top, they die and are “weathered” by the environment and your daily activities. The top “dead” layer is called the stratum corneum. Eventually, the dead cells break away from the epidermis and fall off, making room for newer cells growing up from below. It takes roughly one month for new cells to get all the way to the top layer, meaning the skin you have a month from today will be completely new compared to the skin you have now.