The transcription factor Nanog plays a crucial role in the self-renewal of embryonic stem cells. Previously unclear was how its protein abundance is regulated in the cells. Researchers at the Helmholtz Zentrum München and the Technical University of Munich, working in collaboration with colleagues from ETH Zürich, now report in ‘Cell Systems’ that the more Nanog there is on hand, the less reproduction there is. Every stem cell researcher knows the protein Nanog* because it ensures that these all-rounders continue to renew. A controversial debate revolved around how the quantity of Nanog protein in the cell is regulated.