Studies on the signaling mechanism that control the specification of endoderm-derived organs have only recently begun. While many studies revealed genes involved in the differentiation, growth and morphogenesis of the pancreas through studies of mutant mice, still little is known about how endoderm give rise to specific domains. Although many genes are known to have a role in pancreatic differentiation, growth and morphogenesis, few genes are known to take part in the specification of the pancreas so far. Hallmarks as well as gene markers for early development of the pancreas, which are however still very limited, will be useful for dissecting early events in pancreatic specification. Here, I give a summary on the origin of the dorsal and ventral pancreatic progenitors, signals for inductions, and genes so far known to function in pancreatic differentiation. I also give a future prospect in the use of ES cells and other experimental models, towards a comprehensive understanding of gene networks in the progenitor cells or intermediate cell types which arise during various stages of differentiation.