The skin is the organ with the biggest surface (1,5 - 2m2, depending on height and girth), the heaviest (up to 10 kg) and most multifunctional organ of the human body. It establishes a border between inside and outside, protects the inside from environmental influences, and has functions of representation, communication, and maintaining homeostasis (inner balance). It also performs important functions of metabolism and immunology and has various mechanisms of adaptation available. Due to its close relationship to the psyche, it is also called mirror of the soul.