Both contain specific cell types. At 21 days, the organoids contained all major testicular cell types, including Sertoli cells, organized in a way that closely resembled real testes.

Testicular Leydig cells are the primary source of testosterone in males. Adult Leydig cells have been shown to arise from stem cells present in the neonatal testis. Once established, adult Leydig ...

R. R. Humphrey, A Modification of the Urodele Testis Resulting from Germ-Cell Degeneration, Biological Bulletin, Vol. 48, No. 3 (Mar., 1925), pp. 145-165 ...