Directed differentiation of human pluripotent stem cells (hPSCs) into pancreatic progenitors and beta cells. Left panel, pancreatic progenitors co-expressing the transcription factors, PDX1 and NKX6.1, are considered bona fide beta cell precursors and can be differentiated with a high efficiency from optimized in vitro protocols [21]. Right panel, hPSC-derived pancreatic beta cells expressing INS alone (monohormonal) (arrows) or INS and GCG (polyhormonal) (arrowheads) (Abdelalim’s lab, unpublished data). PSCs, Pluripotent stem cells; DE, Definitive endoderm; PG, Posterior gut tube; PFG, Posterior foregut; PP, Pancreatic progenitors; EP, Endocrine progenitors; PDX1, Pancreatic and duodenal homeobox 1; NKX6.1, NK6 homeobox 1; INS, INSULIN; GCG, GLUCAGON.