What are human nails made of?

Keratin is a tough, fibrous protein that makes up human nails, as well as hair and the outer layer of skin. Nail cells are produced in the nail matrix, then fill with keratin and die, forming the hard, protective nail plate. Unlike bone (rich in calcium) or chitin (the shell material of insects and crustaceans), nails contain no living tissue in the visible plate and no significant mineral content—so they aren’t “calcium” structures. Context tip: Think “Keratin = keratinized coverings”—hair, nails, hooves, and rhino horn are all keratin-based. Memory aid: the “K” in Keratin matches the “K” in (hand) Knuckles and (finger) Knails. Nails typically grow about 3 mm per month, faster on the dominant hand and in warmer seasons.