Aging is an alteration of our physiological capacities that is accompanied by an increased susceptibility to develop a wide range of diseases and which determines in large part our longevity. Despite intensive research on the origin of aging, its etiology is still poorly understood. We discuss here the hypothesis that the telomere shortening, programmed to start at the end of embryogenesis in numerous tissues, couples development with aging by a time-dependent regulation of a set of interconnected processes essential for the somatic maintenance of genome, epigenome, metabolism, circadian clock and immunity.