The natural course of aging, as well as the progression of several degenerative diseases, closely correlates with a loss of adult stem cell quantity and function. Adult stem cells exist in nearly all tissue types in the body and are responsible for maintaining normal tissue turnover and regenerating damaged or injured tissues. Stem cells maintain and repair tissues by reproducing, differentiating into other cell types, and releasing growth and signaling factors to regulate the behavior of nearby cells. Injecting muscle-derived stem cells harvested from young mice can recover the loss of stem cell proliferation and function observed in older mice, and in addition to anti-aging applications, mice with simulated Hutchinson-Gilford progeria syndrome significantly extended lifespan and improved health after stem cell injection. This indicates the therapeutic potential of stem cells from younger donors or stem cells banked early in a patient’s life to ameliorate the symptoms of degenerative diseases or aging.