The production of stem cell derived (SCD) gametes would be of major interest for infertile patients who lack functional gametes. In mice, the production of both SCD oocytes and sperm was successful after an in vivo transplantation step; and more recently the process of spermatogenesis was completely established in vitro starting from pluripotent embryonic stem cells. In human, research regarding the differentiation of stem cells into germ cells has lagged behind, as the risk for tumorigenesis and ethical limitations prohibit in vivo transplantation approaches. It is however speculated that human stem cells in the naive state of pluripotency will need to be used as starting material. The main objective of this project is to investigate the differentiation potential of naive human pluripotent stem cells (hPSCs) towards haploid sperm cells in vitro via the formation of primordial germ cells (PGCs) through an epiblast-like cell stage. These PGC-like cells will be stimulated to enter meiosis in vitro by co-culturing them with human testicular cells, based on a recent protocol in mice. Finally, we want to provide a minimal characterisation on the (epi)genetic and transcriptomic profile of the generated hPSCs, intermediate structures and end products of the differentiation process (i.e. the SCD gametes), to ensure safety for possible future clinical applications.