GrowSperm seeks to train young scientists in a network that joins together the complementary knowledge and expertise of several public and private EU partners from disciplines of physiology, cell biology, molecular biology, chemistry and medicine in the field of male reproduction to investigate three strategies for sperm development: (1) propagation of human SSCs in vitro followed by their transplantation, (2) sperm development in vitro from stem cells or early germ cells, (3) sperm development in human testis tissue grafts in vivo.