So first of all, how does aging occur? Most know that our body are made up of organs, each organ has different type cells and cells tend to reproduce themselves identically or at least that is there intent. So why can't you reproduce perfectly healthy cells as you grow older and why can children can reproduce perfectly healthy cells to the point were they could cut themselves while playing around and heal without leaving a scar?

Aging is caused by free-radicals. Free-radicals describes atoms that are unstable because they is missing an electron. So it doesn't behave the way a healthy atom behaves. Your body already has enzymes to search for free-radicals but that it isn't enough to stop all the free-radicals.  Free-radicals corrupt the DNA so when a cell divides it actually doesn't reproduce an identical healthy cell, instead it mutates. That is the process of how you age and if you have enough mutated cells and they keep growing and multiplying it may lead to cancer. What causes a free-radical? A free-radical is caused by oxidation because at an atomic level oxygen actually breaks up healthy atoms. 

Free-radicals are caused by:

• Pollution
• Smoking
• Stress
• and other factors