Answer
Exposure to ultraviolet rays causes certain skin cells to produce the pigment melanin, which darkens through oxidation.
Work Step by Step
Exposure to ultraviolet rays causes certain skin cells to produce the pigment melanin, which darkens through oxidation. Enough of exposure to the sun and those cells will migrate closer to the skin's surface and produce more melanin, further darkening the skin into a suntan. The pigment melanin absorbs ultraviolet radiation and defends against further penetration of skin tissue.
