Human skin is composed of two primary layers. The outer layer is called the epidermis. It is mostly a protective layer that also keeps moisture in the skin and body. The epidermis is the thinner of the two layers. The inner layer of skin is called the dermis. It is thicker and provides the protection and support that the skin provides the body. The two layers are separated by the basement membrane.
Fingerprints are produced by the epidermis. They are caused by the friction ridges on the outermost layer of the skin. These ridges have a unique shape that can be used to identify people. Oil and sweat secretions leave the marks of these ridges on smooth surfaces, thus leaving a fingerprint.