Nails are produced by living skin cells in the fingers and toes. They are composed mostly of keratin, a hardened protein also found in the skin and hair.
Nails grow from an area called the matrix that lies under the cuticle. As older cells grow out, replaced by newer ones, they are compacted and take on a flattened, hardened form. The average growth rate for nails is only 0.0039 of an inch each day, although individual rates depend on age, time of year, activity level and heredity. Nails grow faster on fingers than toes, and they also grow faster on your dominant hand. Women’s nails grow slower than men’s, except possibly during pregnancy and old age.