Intrinsic Aging or Chronological Aging involves changes in the skin that are alone due to time and will be noticable by the age of 50 to 60 years. If you were to get minimal sun exposure this skin would look pale and smooth with fine wrinkles and some dryness.  Some of this is a result of oxidative  cellular metabolism. that forms Reactive Oxygen Species (ROS) .   ROS  causes cumulative damage to cells such as damage to cell membranes, DNA and enzymes.  With each cell division there is also shortening of the telomere in DNA and when the length becomes critically short, the cell is signaled to stop the cell cycle or to die. This contributes to the depletion of cells in aging.  Growth Factors and Hormones also decline with age such as oestrogen, testosterone, and dehydroepiandrosterone (DHEA), which are involved in the reduction of skin thickness, elasticity,  wound healing, and an increase in dryness.  This is all due to loss of barrier function and decrease in collagen and elastin production.  These factors visually are described as xerosis, skin laxity and wrinkles and the formation of benign leisions. Intrinsic Aging is a process of loss and body processes are on a decline.  Intrinsic Aging can be exacerbated by the sun, extrinsic or photoaging.