Fingernail. Coloured scanning electron micrograph (SEM) of the tip of a finger, including the nail. The top layer of the skin is composed of dead keratinised cells that are continuously sloughed off and replaced with new cells from below. The nail plate, the visible part of the nail, is composed of a hard translucent form of the protein keratin. Magnification: x5 when printed at 10 centimetres wide.