An impressive review in thus week's NATURE surveys the complexities of the causes and mechanisms of cellular senescence. Of particular interest is the increasing evidence for a critical role of senescent cells in the aging of tissues and organs. This can come about in many ways including loss of stem cell capabilities. However, one key aspect is the ability of senescent cells to produce inflammatory factors that then lead to tissue degeneration. The growing information on the link between cell senescence and aging opens the door to possible therapeutic approaches that might slow down the decline of functions with age.