Lips are composed of three layers of skin (the innermost, subcutaneous layer, the middle, dermis layer and the outermost, epidermis layer) just like the rest of our face. The cells within these layers are responsible for producing the elastin and collagen fibers that provide the full, plump shape and smooth texture that almost all lips enjoy in youth. These fibers are produced by our skin cells regularly, being lost and replaced constantly, and do the work of helping our skin to rebound from stretching (elastin) and maintain firmness or plumpness (collagen). Over time, our body becomes less capable of generating elastin and collagen and, because of their absence, common signs of aging — like lip wrinkles, fine lines, sagging or thinning — become noticeable.