Research team led by Prof. Cédric Blanpain has identified the mechanisms that regulate mammary gland development. Using a combination of lineage tracing, molecular profiling, single cell sequencing and functional experiments, A. Wuidart and colleagues demonstrated that mammary gland development is initiated by multipotent progenitors during the early steps of embryonic mammary gland morphogenesis, whereas postnatal mammary gland development is mediated by lineage-restricted stem cells.