Skin is the outer covering on the bodies of animals or human beings. It protects muscles, bones and the internal organs. As it is in direct contact with the environment, it protects the body from viruses, parasites, etc. Other functions of the skin are insulation, temperature regulation and sensation. It also supports the production of important vitamins such as vitamin D and vitamin B. The colour and type of skin varies across populations. There are three main layers of the skin: epidermis, dermis and subcutaneous.