Our fingernails are mostly made from a protein called keratin, used all over the animal kingdom in claws, hair, nails, horns and skin. They are also called digital appendages and their structure is broad, slightly curved and mostly cover the top surface of our fingers.

Our hand and feet are important in daily life, but the fingers and toes are also very sensitive parts of the body, especially the tips which allow also much of the feeling and sensitivity.

The fingernails are designed to protect the tips of the fingers and toes, against things like bumps, burns, cuts and other hazardous situations but without limiting the motion or sensitivity (that is why the fingernails are only on one side).

In other species, this structure is slightly different and probably evolved in a way that best fit their needs for a particular environment. For example, crocodiles have a thimble-shaped structure that covers the whole tip of their digits, cats have claws that help them hunt and climb, hawks and owls have talons, specialized for prey capture, and horses and cows have hooves that protect their feet.