The skin is mainly composed of two layers: the outer epidermis and the inner dermis. The effective part is epidermis, whether it is suntanned or imitated. The epidermis also has a layered structure. The deepest layer of the epidermis is called the basal layer, which will be affected by exposure to the sun. The stratum corneum (keratinized layer) is the outermost layer of the epidermis-this layer is influenced by most sun-free tanning products.