The epithelium of glandular tissue such as mammary and prostate glands consists of adjacent layers of luminal and basal cells. During development, stem cells in the basal layer contribute to the formation of both cellular layers, but in adults, these stem cells lose their multipotency. This loss can be reversed when there is damage to the tissue, allowing the basal stem cells to contribute to the restoration of both layers. In this issue, Cédric Blanpain and his colleagues show that the potency of basal stem cells is directly regulated by luminal cells secreting TNF proteins, which act as an inhibitor of basal stem cell multipotency. The cover image shows a mammary gland branch with basal cells (red) and luminal cells (green).