Not all cell types and tissues age equally—some are selectively vulnerable to aging and may set the healthspan for the entire organism. While growing evidence suggests tissue-specific differences in the rates of aging, no individual cell population or tissue has been shown to orchestrate the pace of organismal aging. Our lab is interested in identifying these critical cell populations that constrain lifespan and developing new molecular tools to interrogate their function. By identifying such cells, the Segel lab hopes to identify new therapeutic interventions to treat a range of aging-associated diseases, and, ultimately, identify the tissues, cells, and genes that are under selective pressure in the evolution of mammalian lifespan.