1.  Epidermis
2.  Dermis
3.  Subcutaneous Layer

The epidermis is the outermost layer (the layer you can feel and see). The epidermis itself consists of four layers. Several kinds of skin cells are formed in the innermost layer (the basal cell layer or stratum germinativum), and push their way to the outermost layer (the horny layer or stratum corneum). In the process, the live cells change into dead, hard, flattened cells. Dead cells on the surface are constantly being shed or rubbed off, making way for newer cells from below.

The horny layers in the epidermis is the body's first layer of defence. It consists primarily flattened cells called keratinocytes joined together by skin lipids, which are combination of four fats. Think of a wall made up of bricks and mortar, and you get some idea of the structure of the horny layer. The horny layer prevents most substances from difussing into lower layers, only a few very light oils and skin identical substances can penetrate deeper.

Besides Keratinocytes, the basal cell layer also produces melanocytes, cell that produce a substance called melanin. Melanocytes are stimulated to produce melanin by the ultraviolet (UV) rays in sunlight. Melanin is a dark pigment which blocks UV rays. The greater the exposure to sunlight, the greater the production of mealnin.

The dermis is the foundation of the skin. It contains blood and lympatic vessels, sweat glands, hair folicles, sebaceous glands and nerve endings. These are held together by collagen and elastin fibers, which together give skin its strength and flexibility.

Blood and lymphatic vessels in the skin do more than just bring nutrients to skin cells and carry away wastes. They also act as heat regulators, somewhat like the radiator in your car. When you feel hot, these vessels dilate and carry more fluid, radiating heat to the outside. When you feel cold, they contract, reducing the flow of fluid to the body's surface to preserve body heat. Sweat glands also help regulate temperature by producing sweat which evaporates from the surface to lower skin tempratures.

Hair follicles produce hair. Associated with them are sebaceous glands, which produce sebum, which forms a majority of the lipids in hair and skin. An excess of sebum makes your skin look and feel oily.

The dermis is also the biggest storehouse of a substance called sterol (Greek for 'solid alocohol') which in itself is of no use to the body. It is, however, converted into vitamin D by the action of Ultra Violet rays in sunlight. Since this is the major source of the body's vitamin D, a certain amount of sunlight is good for the body.

The subcutaneous layer (meaning 'below the skin') layer is a fatty region that is not always considered part of the skin. Its health however, has a direct bearing on the health of the dermis and the epidermis.