When people age what changes make them look older?

the human body cells divide 50 times throughout their lives, each time they divide, they become damaged and are unable to repair themselves, this is what causes aging, the wrinkles and saggy faces are caused by these damaged cells, but the changes in the teenage years are caused by hormones being released which build up the cells making the tissues and bones increase length and density, hope this helps but you'd be safer looking it up