Aging is typified by a gradual loss of physiological fitness, leading to deteriorated functions and enhanced vulnerability. Such deterioration is the key risk factor for critical pathologies such as cancer, diabetes, cardiovascular and neurodegenerative disorders, and many other maladies. Various studies have examined how aging takes place and how it is controlled by sophisticated cellular and molecular mechanisms at different periods of life. Multiple factors involved in the aging process and longevity have been described. The finding that the rate of aging is regulated, at least to a certain extent, by genetic routes and biochemical processes conserved in evolution has triggered remarkable advances in aging research. Aging is basically damage that accumulates over time and is manifested in certain physiological forms, considered as the hallmarks of aging. A hallmark of aging is a distinct attribute that occurs upon normal aging and correlates with the decline in biological function and increased risk of age-associated diseases. Moreover, in order to qualify as a hallmark, the attribute needs to play a causative role in the process of aging. The definition of nine molecular and cellular hallmarks of aging in 2013 provided a background framework to channel future aging research. These hallmarks included: