The pancreas is a mixed (exocrine and endocrine) glandular organ that is important for food digestion and glucose homeostasis. Developmental anomalies or disorders that affect normal pancreas homeostasis may cause various life-threatening diseases such as pancreatitis, diabetes, cystic fibrosis, and pancreatic cancer. In the past two decades, an increasing number of studies have begun to unravel the molecular and cellular mechanisms regulating mammalian pancreas organogenesis. The information extracted from these studies should be valuable both, to better understand the etiology of some pancreatic diseases, and to design new therapeutic tools to cure those diseases. A recent study reported expression of the homeodomain transcription factor Prox1 in the presumptive pancreatic region of mouse embryos. This finding raised the possibility that, similar to other tissues, proper pancreas development requires the function of Prox1. The studies described in this book sought to uncover the role of Prox1 during mouse pancreas organogenesis.