Keratin

Nails are a part of the human and animal body. They tend to grow at the tips of the hand on feet. On humans, at the fingers and toes. Horses, the hoof is one big nail, etc. Nails are made of keratin. Keratin is dead, hardened skin usually used for protection. If, for instance, you touch underneath your nail, it can cause extreme discomfort. It lines the outer skin layer as well, and lines hair follicles and horns. The cells that harden into keratin go through a process called keratinization. Keratin protects us from cuts, and pressure. If we had no keratin, we would have to live a much more careful, secluded life.