Skin layers. Coloured light micrograph of a section through human skin layers. The top layer is the stratum corneum (flaky, orange), a cornified layer of the epidermis that is composed of flattened, dead skin cells that form the surface of the skin. The dead cells from this layer are continuously being shed and replaced by cells from the living epidermal layer below (stratum germinativum, yellow). The lowest layer seen here is the dermis (red, bottom). This is a thick layer of fatty and connective tissue that supports and nourishes the epidermis. The skin is the body's largest organ, accounting for around 15 per cent of the body's weight. Magnification: x200 when printed 10cm wide.