Nails and hair are essentially made up of a tough protective protein called keratin. While the hair grows in a hair follicle, nails grow from the matrix (the base of the nail bed). Both the hair follicle and the nail matrix are made of epithelial cells and will continue to grow as long as they receive nutrition and remain healthy. As the epithelial cells within the follicle and matrix multiply, the older cells are pushed out, upwards through your skin. They die and harden, thus turning into hair or nails. This process, called keratinisation, makes your hair and nails grow.