Baby's nail. Coloured scanning electron micrograph (SEM) of a section through a baby's nail. Nails are keratinised structures (they contain the protein keratin) made up of dead tissue bound together to form a hard, protective structure on the tips of the fingers and toes. The growth of a fingernail is similar to that of a hair, another keratinised structure that grows on a human body. Nails form a layered structure, with the bottom layer attached to the skin. Several layers are seen here.