A look at the international race to create human eggs and sperm in the lab

In which we meet the pioneers of one of the most exciting — and controversial — fields of biomedical research: in vitro gametogenesis, or IVG.

The goal of IVG is to make unlimited supplies of what Hayashi calls "artificial" eggs and sperm from any cell in the human body. That could let anyone — older, infertile, single, gay, trans — have their own genetically related babies. As such, the field opens up a slew of ethical concerns.

But that isn't stopping researchers from pressing forward.

So, this episode NPR science correspondent Rob Stein gives us a glimpse into the global race to create the first artificial human embryos to see how the competition is unfolding.