Skin surface comparison. Coloured 3-D light micrograph comparing the skin of a 6-year-old (top) with that of a 43-year-old (bottom). The outermost surface is composed of dead and dying skin cells from the underlying epidermis, which help to protect the delicate epidermal cells from the external environment. A sweat gland filled with sweat (lower left) and an empty (dry) sweat gland (lower centre) can be seen on the older skin. Magnification x25 when printed 10 centimetres wide.