The top layer of skin is the epidermis. The epidermis is thin, averaging only millimeters thick (about 1/100 of an inch). It protects the deeper layers of skin and the organs of the body from the environment. Keratinocytes are the main cell type of the epidermis. These cells make an important protein called keratin that helps the skin protect the rest of the body. The outermost part of the epidermis is called the stratum corneum. It is composed of dead keratinocytes that are continually shed as new ones form. The cells in this layer are called squamous cells.
