The adult pancreas lacks stem cells, and consequently, differentiation of pancreatic endocrine cells has been restricted to embryonic development or experimental manipulation. In this issue of Cell Stem Cell, Sancho et al. (2014) show that pancreas-specific loss of the ubiquitin ligase Fbxw7 stabilizes an endocrine-specific transcription factor, Ngn3, thus inducing in vivo β cell neogenesis.