The epidermis is divided into three sublayers. The horny layer is the tough, waterproof cover made up of dead cells, which are continuously shed as new cells come up from below. This is the layer that most skin care products affect, improving the look of the skin by temporarily plumping the dead skin cells. This distributes light more evenly, creating the appearance of smoother, more radiant skin, but in order to actually improve the condition of the skin, you would need a substance that would be able to penetrate this outer layer of skin. The build up of dead skin cells on the outer layer can lead to dull skin and clogged pores.
Exfoliation can help remove the dull skin, but only if the skin has been sufficiently loosened.
Moisturizers also target this layer, working to trap, or, in some cases, capture moisture to keep the keratinocytes plump and smooth. The basal layer births the new skin cells that will eventually mature into squamous cells. This layer contains melanocytes, the cells that give pigment to your skin, known as Melanin. Exposure to sunlight cause the melanocytes to produce more melanin in an attempt to protect the dermis below. This is what gives your skin a tanned appearance after sun exposure.