The skin — the largest organ of the body — is made up of a thin outer layer (called the epidermis) and a thicker outer layer (called the dermis). Below the dermis is the subcutaneous tissue, which contains fat. Buried in the skin are nerves that sense cold, heat, pain, pressure, and touch. Sebaceous glands secrete a lubricating substance called sebum. Deep within the skin are your sweat glands, which produce perspiration when you are too hot.
Source: AMA's Current Procedural Terminology, Revised 1998 Edition. CPT is a trademark of the American Medical Association.