Revealing the mechanism of adult organ maintenance and regeneration after injury is fundamental to our understanding of the pathogenesis of diseases. Considering the results of pulse and chase experiments using inducible insulin-Cre or Elastase-Cre, and more recently HNF1b-Cre, adult pancreatic cells (beta, acinar, and duct cells) seem to be maintained by the self-duplication of the existing cells, while there is still a dispute about whether adult beta-cells are supplied from the duct cells. Here we describe the advantages and pitfalls of Cre-mediated genetic lineage tracing experiments in the analysis of embryonic organogenesis and adult organ maintenance of the pancreas. This experimental technique enables us to visualize the specific cells and their progeny in vivo, and the combination of lineage tracing and other experimental procedures provides us with more detailed information on the mechanism of organogenesis and adult organ homeostasis.