Tanning beds use ultraviolet light (UV) to tan people. There are three types of UV- UVA, UVB and UVC. Tanning beds are designed to concentrate optimal levels of UVA, in conjunction with very low percentages of UVB, on the outermost layers of the skin so as to stimulate the production of Melanic pigment, which is slightly pink in it's dormant state, and cause it to turn brown after excretion. The more melanin cells that are present in the skin determines the amount of pigment that will be excreted and distributed, and therefore the extent of the tan. Tanning beds are designed to filter out UVC as this is a harmful type of UV.