Skin is a resilient protective layer of cells protecting the muscles and organs of animals. Skin is formed in several layers, for optimum performance. Living skin is a material of exceptional quality, with good temperature tolerance and insulating ability.
Mammalian skin often contains hairs, which in sufficient density is called fur. The hair mainly serves to augment the insulation the skin provides. On some animals the skin is very hard and think, and can be processed to create leather.
Damaged skin will try to heal by forming scar tissue, often giving rise to discoloration and depigmentation of the skin.
The skin is often known as "the largest organ in the human body", since it weighs more than any single internal organ.
The skin is subject to constant attack from without, and so can be afflicted by numerous ailments, such as: