Our recent data pinpoint a window of time in human and pig kidney organogenesis that may be optimal for transplantation into mature recipients. ‘Window’ transplants are defined by their remarkable ability to grow, differentiate and undergo vascularization, achieving successful organogenesis of urine-producing miniature kidneys. The transplanted tissue shows no evidence of trans-differentiation into non-renal cell types or tumorogenicity, and displays reduced immunogenicity compared to its adult counterparts. Very recently, we demonstrated that this approach can be extended to transplantation of embryonic pig liver, pancreas, and lung tissue. Furthermore, it was demonstrated that E42 pancreatic tissue is optimally suited for induction of normoglycemia in diabetic mice. These results emphasize the importance of selecting precursors of the correct gestational age for optimal growth and function, and with reduced immunogenicity, and provide a proof of principle for the curative potential of E42 embryonic pig pancreatic tissue for transplantation in diabetic patients.