Intrinsic or chronological ageing is the natural ageing process that you were born with. In other words, it's in your DNA & it is an inevitable process. Intrinsic ageing is affected by free radical damage, hormonal shifts, and your body's inability to completely repair this damage.
Intrinsic ageing is a continuous process that begins in your mid-20's, and will not be evident for decades. During your 20's, collagen and elastic production begins to slow down. The dead skin cells do not shed as quickly and your cell turnover decreases. Be aware that the cells, tissues and organs within your body age as well.
Extrinsic ageing is influenced by your lifestyle choices and your environment. Bear-in-mind that this component to ageing is in your control and it will magnify intrinsic ageing, usually leading to premature ageing.
Most premature ageing results from sun exposure, repetitive facial expressions, gravity, sleep habits, over indulgence of sugar & alcohol, dietary choices, smoking, stress and pollution. Age associated changes include skin thinning, sagging, fragility, wrinkles, and pigmentation changes.
While you can't change your DNA's intrinsic aging process, you can influence and control the extrinsic ageing component. Extrinsic ageing speeds up your skin's natural ageing process.