Our 60 trillion cells will progressively age; this is what scientists call ‘gradual senescence’ which is essentially the growing inadequacy of the organism’s defenses, and especially our DNA’s, when faced with accumulating damage. When we age, cells also lose the capacity to multiply. This is essentially because of the shortening of our telomeres, which are no longer able to protect our chromosomes. This is what scientists call ‘replicative senescence’. A third player completes this aging trilogy: stem cells, which are essential to cell renewal and proper maintenance. Stem cells are no longer able to get the job done if their DNA is seriously damaged and their telomeres are shortened. Our stem cell supply then shrinks, which compounds the problem.