The progress achieved in Japan through experiments on mice has shown the way forward, but replicating these results in humans will pose technical, ethical, and legal challenges

Gametogenesis is the process by which gametes — male and female sex cells — are formed. In nature, it occurs inside the testes and ovaries, starting from progenitor cells that receive a variety of signals. Replicating the process in vitro is already possible in mice, albeit with low efficiency. Some specialists expect that within a decade, knowledge and technology will have advanced enough to apply these methods to humans, producing both sperm and eggs from cells taken from other parts of the body, and from individuals of either sex. This could allow infertile couples to have genetically related children without external donors, but it would also open the door to troubling new scenarios.