The skin is the largest organ of a human body.  It covers and protects the body against injury or infection, regulates body temperature and water content, and senses touch, heat or cold.

The skin has 3 main layers: epidermis, dermis, and hypodermis.

The epidermis is the superficial most layer which itself consists of 5 different sublayers. There are three main types of skin cells occupying these sublayers: basal cells, squamous cells and melanocytes.

Basal cells are the round cells located at the bottom (or basal) sublayer of the epidermis whereas squamous cells are the flat cells at the top of the sublayers. Melanocytes are the cells in the bottom of the epidermal sublayers that produce melanin, a brownish pigment making up human skin tone. Melanin both absorbs and scatters UV radiation and thus protects skin from the mutagenic effects of the solar radiation. When damaged and genetically altered by UV radiation from sun rays or tanning bed, any of these cells can uncontrollably multiply and turn into skin cancer, such as basal cell carcinoma, squamous cell carcinoma, or melanoma.