The dermis is a thick, supple and sturdy layer of connective tissue and makes up about 90 percent of the skin's thickness. The border between the epidermis and dermis forms a waving structure allowing them to be tightly adhered together. This transitional zone is the most complex region of the skin, with some of the rare genetic skin conditions having disorders here.

It is a dense meshwork of fibrous tissue, collagen and elastin fibers, forming a strong framework holding up the epidermis on top.

The cells called Fibroblasts in the dermis make the collagen and elastic fibers. When the skin ages, these fibroblasts will shrink in size, have a lower metabolic rate, and the production of collagen and elastic fibers will decrease. The accumulated sun exposure will make the fibroblasts become irregular and plump, with production of unhealthy collagen. It also directly damages the elastic fibers. This is the Photoaging.

Collagen

This is a very tough protein. It forms as bundles of slightly wavy structures interlocking each other in young healthy skin, giving a firm texture.

When the skin ages, the amount of collagen decreases, and their alignment becomes irregular. This makes the dermis lose its bulk and become thinner.

Elastic Fibers

These confer and maintain the elasticity of the skin. Younger skin is firm and elastic, while aged skin is thin, saggy, and filled with wrinkles, largely because of the loss of elastic fibers.

Sun aging actually increases the amount of elastic fibers, but in an unhealthy way. They become plump and damaged inside, and are arranged in a disorganized manner. The result is a piece of skin feeling like a piece of thick leather.