The ultraviolet (UV) rays that come from the sun are classified into different wavelengths, UVA, UVB and UVC. The wavelengths of the UVC rays, which are 100 to 280 nanometres (nm) in length, are absorbed by the earth's atmosphere and do not concern us. The majority of UV radiation reaching the earth's surface is UVA with a small component of UVB. The UVB rays mainly affect the outer layers of the skin and are mostly responsible for our sunburn and risk of skin cancer. They consist of shorter wavelengths (280 to 320 nm) and are mostly absorbed by the epidermis (outer layer of the skin). The UVA rays consist of longer wavelengths (320 to 400 nm) than the UVB, and penetrate deeply into the skin triggering melanin production, the pigment that gives us our tan. They are also the ones which cause ageing, wrinkling and loss of elasticity.