Epidermis
The Epidermis consists of five layers (from the base upwards)
Stratum Basale
Stratum sponosum
Stratum granulosum
Stratum Licidum
Stratum Corneum (horny layer)
It is a defense against:
Water and moisture loss
Diseases
Chemicals damage (soaps/unfriendly ingredients)
Sun damage (UV)
Mechanical protection (bacteria and water)