This cross section shows how complex the skin is built.

The stratum corneum is imperceptible and worn out relatively quickly and therefore must constantly from the lower cell layers are adding. Within approximately four weeks in this way regularly all cells of the epidermis renewed. Under the germ layer is a border zone, also called basal, as the weather angle of numerous skin diseases to be.
Immediately on the basal found branched tree pigment cells, which the skin pigments (melanin) to produce and the surrounding horn cells of competence. The color of the skin by the number, size and distribution of skin pigment determined. The actual function of pigment cells lies in the sun (protection against UV-light) of the horn cells, the pigment production by UV radiation stimulated (sun tanning). 
If a pathogen, the stratum corneum to penetrate, he will be just above the basal star of the Langerhans cells, the first outpost of the immune system, intercepted. These cells are the guardians of the body's own defenses and promptly alert other immune system cells (T lymphocytes).