Naïve T cells develop in the thymus. Although thymic function declines with age, T cells are persistent throughout the human life span. Thome et al. examined human lymphoid tissues from donors ranging from 2 months to 73 years in age. They found that, although the number of double-positive thymocytes and recent thymic emigrants dropped in individuals >40 years of age, naïve T cells were functionally maintained in the lymph nodes. There was minimal overlap in clonotype between the lymph tissues, suggesting that lymph nodes may maintain a diverse set of T cell specificities. These data suggest that location really does matter—tissue compartmentalization and homeostasis are critical for maintaining naïve T cells throughout the human life span. To read the entire paper in Science Immunology, click here.