Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Senescence or biological aging is the endogenous and hereditary process of accumulative changes to molecular and cellular structure disrupting metabolism with the passage of time, resulting in deterioration and death. Senescence occurs both on the level of the whole organism as well as on the level of its individual cells. Albeit indirectly, senescence is by far the leading cause of death - f the roughly 150,000 people who die each day across the globe, about two thirds—100,000 per day—die of age-related causes. Learn more about senescence, its causes and effects in this book.