Skin

"The skin is the largest organ of the body, with a total area of about 20 square feet. The skin protects us from microbes and the elements, helps regulate body temperature, and permits the sensations of touch, heat, and cold.
Skin has three layers: The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone.
The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands.
The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue.
The skin’s color is created by special cells called melanocytes, which produce the pigment melanin. Melanocytes are located in the epidermis."

Wart

Warts are small, usually painless growths on the skin caused by a virus called human papillomavirus (HPV). Most, but not all, are generally harmless. Warts can be disfiguring and embarrassing. Sometimes they itch or hurt (particularly on the feet). Some warts spread through sex. All warts can spread from one part of your own body to another. They may spread from one person to another, but this is uncommon. Treatment is available if you do not like how the wart looks or if it is painful.