The top layer of skin is called the epidermis, the second layer is the dermis, and the third layer is the hypodermis. The skin is the body's largest organ, and it offers the first line of protection against bacteria and other harmful substances.
The skin helps the body regulate heat and provides the sensation of touch. The outermost layer, the epidermis, is waterproof and provides humans with their skin tone and color. Hair follicles and sweat glands are located in the dermis, and the hypodermis is made up of fat and connective tissue. The average person has about 20 square feet of skin.