Why skin changes as you age?

Being in my 20s, I'm concern with skin aging. I was on iQ Derma website and learned that skin aging is caused by a combination of Intrinsic, Environmental, and Mechanical factors.

Intrinsic Aging: As a person ages, skin biology changes. Every person's skin undergoes the same changes at a microscopic or cellular level: Cell function slows down, leading to a break down of structural proteins and a decrease in your skin's ability to repair itself. This is called Intrinsic Aging. While we are all pre-programmed to experience Intrinsic Aging, the extent and speed at which these changes occur varies from person to person depending on genetics.

Environmental Aging: The role of the sun cannot be overstated as the most important cause of prematurely aging skin. As much as 80% of premature skin aging is caused by sun damage. Both UVA and UVB rays cause harm leading to wrinkles and pigmentation problems such as uneven skin tone, blotchy skin, and age spots.
Sunlight impairs collagen fibers, stimulates production of enzymes called metalloproteinases (MMPs) that further degrade collagen, and contributes to over-production of oxidants, also called free radicals. These are unstable molecules that can destroy skin cells, causing skin to "spoil."
Furthermore, the role of sun exposure in skin cancers is proven. This is another reason to reduce the amount of time you spend in the sun without protection. Wear a broad spectrum sunscreen to minimize risk and help prevent further damage to the skin.

Mechanical Aging: Repetitive facial expressions caused by small muscle contractions stretch skin and break down structural proteins. The effects of these expressions accumulate over time, leading to frown lines (those between the eyebrows), laugh lines (wrinkles at the corners of the mouth), and crow's feet (lines that radiate from the corners of the eyes). Gravity also contributes the drooping or sagging skin by pulling down on the jowls eyelids.

Au revoir