The skin has many functions; it:

• protects the internal organs of the body from injury, such as damage from falls
• protects the body from ultraviolet light from the sun
• helps to regulate body temperature
• gets rid of waste substances.

The skin is divided into two main layers. The layer nearest the surface is known as the epidermis and the layer underneath this is known as the dermis. Melanoma develops from cells called melanocytes. These cells normally lie in the lower part of the epidermis and produce a pigment called melanin. Melanin is responsible for the colour of our skin. Moles are groups of melanocytes that lie close together. Most pale-skinned people have about 20–30 moles on their skin.