Pluripotent stem cells (PSCs) can make all the tissues including gametes such as sperm and eggs. Researchers from the National Institute for Physiological Sciences in Japan report a robust method for the generation of gametes from PSCs using the body of rats that cannot make gametes. Notably, they successfully generated mouse PSC-derived functional spermatids in rats. This approach will become a useful system for the generation of PSC-derived germ cells in the future.