A special growth area called the matrix at the base of the nail controls the speed of the growth of the fingernails. The matrix lies in a deep groove in the dermis (the thick inner layer with nerves and blood vessels) of the skin. The matrix makes a dead, hoof-like protein, called keratin - the material which makes the nail. It makes nails constantly from birth to death at an average rate of 0.004 inches (0.1mm) each day, or 1.5 inches (36.5mm) in a year. However, the matrix does not make nails at a steady rate. Nails grow faster when it's warm, when we're young, when we apply pressure to the nails while playing on the piano or biting, cutting, filing, polishing or scrubbing them. Nails grow slower when the matrix is short of blood or when we suffer from malnutrition or have a high fever.
