The epidermis is the outermost layer of the skin that consists of three types of cells, keratinocytes, melanocytes, and langerhans cells. The predominant cell in the epidermis is the keratinocyte, which makes the protein karatin. Once these cells have divided and matured they move to the upper layer of the epidermis which is called the stratum corneum; this is where they die and become hardened proteins and lipids forming a protective crust. The dead cells from the stratum corneum are constantly sloughed off and replaced with new ones. As we get older this process tends to slow down which is when exfoliating your skin, such as with a loofa sponge is extremely helpful.
The melanocyte cells in the epidermis produce melanin, which is the pigment that gives the skin its tone and color. Melanin is found not only in the skin but the eyes and hair as well. Finally the langerhan cells are the cell that are in direct relation to the immune system. They prevent unwanted foreign substances from entering through the skin.
The dermis is the middle layer of the skin that consists of two layers the upper and lower. The upper layer is the papillary and the lower is the reticular dermis. The dermis contains blood vessels, nerve endings and sebaceous glands that are always producing sebum. Sebum is the skins natural oil that rises to the epidermis lubricating and protecting the skin.
Finally, the hypodermis (subcutaneous fat), is the bottom layer of the skin made mostly of fat. This is where the skin is attached to the bones, and muscles, supplying them with blood vessels and nerves. The subcutaneous fat acts a heat insulator and shock absorber protecting the tissue below from trauma and cold.