Melanin is the pigment that helps protect human skin cells from ultraviolet radiation.
Melanin is produced by specialized cells called melanocytes, which are located mainly in the basal layer of the epidermis. Melanocytes package the pigment into melanosomes and transfer them to nearby keratinocytes. These pigment-containing structures can absorb and scatter some ultraviolet energy before it damages cellular DNA.
Human skin colour reflects the type, amount, and distribution of melanin, as well as how melanosomes are handled in the skin. Sun exposure can stimulate increased melanin production, producing a suntan, but tanning does not make ultraviolet radiation harmless.
Melanin also contributes to hair and eye colour. It is not the same as hemoglobin, which gives blood its red colour, or bilirubin, a yellow pigment produced during breakdown of heme. Sun protection remains important because melanin provides only limited natural protection.