Homeostatic capacity is the capability of systems to self-stabilize in response to stressors. A simple way to visualize homeostatic capacity is to imagine a WeebleTM, the popular self-centering children's toy. For organisms, it is life's foundational trait—itself comprised of a hierarchy and network of traits—endowed by nature and shaped by selection. Because the trait is inborn and so pervasively effective, feeling healthy feels like "nothing" when we are young. We become aware of it only after we start losing it midlife. Roller-coaster rides begin to leave us nauseated instead of joyous. We can't tolerate hot or cold weather like before. Sunny days feel too bright and reading menus in low lights becomes more difficult. Recovering from stressors—a late night, hangover, or injury—suddenly take far longer than it used to, if at all. Consider changes that we can't feel. When we are young, homeostatic capacity returns elevated blood glucose and blood pressure to base levels. As homeostatic capacity erodes with age, those levels may no longer self-tune. We call these conditions diabetes and hypertension, respectively. Indeed, the panoply of ailments associated with aging may be epiphenomena of eroding homeostatic capacity. If so, could restoring homeostatic capacity end or reverse aging?