Skin

Skin is the main external organ measuring 0.5 - 4 milimetres thick, concealing blood and other internal organs inside the body. It is usualy exposed on all animals. In most animals, the skin as the eyelids are used to cover the eyes in a short amount of time and moisturise them. But, with animals that don't have eyelids (such as lizards) lick them with their tounge.