A nail's a horn-like structure at the end of an animal's finger or toe. See also claw. Parts of the nail Fingernails and toenails are made of a tough protein called keratin and have many different parts: Matrix This's the only living part of the nail. It's situated behind and underneath the Nail Fold and produces protein keratin which makes up the Nail Plate. If the matrix's ever damaged in any way, it'd affect the Nail Plate growth. Eponychium This's the dead skin that forms around the cuti… (More on Toenail)