Learning how the skin functions begins with an understanding of the structure of the three layers of skin: the epidermis, the dermis, and subcutaneous tissue. The Epidermis. The epidermis is the outermost layer of the three layers of skin. Its thickness depends on where it is located on the body. For example, it's thinnest on the eyelids (half a millimeter). On the palms of the hands and soles of the feet, it's thickest (1.5 millimeters). There are five layers of the epidermis: 1  Stratum basale: This bottom layer, which is also known as the basal cell layer, has column-shaped basal cells that divide and push older cells toward the surface of the skin. As the cells move up through the skin, they flatten and eventually die and shed.