(A) Solar et al. (51) performed pulse-chase experiments using the Hnf1bCreER^T2;R26R mouse model. Hnf1β-positive cells give rise to all pancreatic lineages when recombination was induced prior to secondary transition. When pulse labeled between E13.5 and E15.5, progeny cells were found only within the endocrine and ductal compartments. Induced at E18.5, Hnf1β-positive cells are located exclusively within ducts. (B) Furuyama et al. (52) demonstrated with their Sox9^IRESCreERT2;R26R model that Sox9-positive cells give rise to acinar, ductal, and endocrine cells when induced at E16.5 and P1, respectively. Any time after P7, Sox9-positive cells repopulate the acinar and ductal compartment. (C) Kopp et al. (53) labeled Sox9-positive cells with a transgenic approach, using Sox9CreER^T2;R26R mice, and confirmed that Sox9-expressing cells give rise to all pancreatic lineages when induced between E8.5 and E18.5. When analyzing pancreata that were labeling at P5, recombination was observed in ducts and endocrine cells. TM, tamoxifen.