The epidermis is the superficial layer of the skin. Its thickness is variable and depends on the location. The epidermis is made up of stratified, keratinized, squamous and non-vascularized epithelial tissue. It covers the dermis which is very vascularized and ensures the nutrition of the epidermis by diffusion. The embryological origin of the epidermis is in the ectoderm, which is the external layer of the embryo.

The main constituents of the epidermis are the keratinocytes, which represent 80% of the epidermal cell population. Keratinocytes are so called because they produce large quantities of proteins, the keratins. They are extremely dynamic cells that undergo permanent proliferation and differentiation, at the end of which they are transformed into dead cells that are eliminated by the phenomenon of desquamation. The other cells that make up the epidermis are melanocytes, immunocompetent cells (Langerhans cells and lymphocytes) and Merkel cells.