47 THE DREAM OF ELIXIR VITAE João Pedro de Magalhães, Ph.D. Human aging is a universal process of loss of viability and increase  in  vulnerability.  Although  so  far  the  underlying mechanisms of aging remain largely a mystery, it is reason- able to expect that we will eventually understand the human aging  process.  Possibly  during  this  century,  we  will  know what changes occur in a human being from ages 30 to 70 to increase the chance of dying by roughly 32-fold. Yet even if researchers detail those changes, even if researchers identify the causal molecular and cellular mechanisms responsible for human aging, this will not necessarily lead to a cure for aging. HIV was identified as the cause of AIDS over 20 years ago and we still cannot cure AIDS. [1] So to delay aging, not to mention to stop or reverse the human aging process, will be a monumental task. It is true that we still do not know in detail what changes occur as human beings age, but it is equally true that the most important question in studying aging is not why we age but how can we fix it.