Mouse embryos have been grown on the International Space Station and developed normally in the first study indicating that it could be possible for humans to reproduce in space, a group of Japanese scientists said.

The researchers — including professor Teruhiko Wakayama of the University of Yamanashi’s Advanced Biotechnology Center and a team from the Japan Aerospace Space Agency (JAXA) — sent frozen mouse embryos on board a rocket to the ISS in August 2021.

Astronauts thawed the early-stage embryos using a special device designed for this purpose and grew them on the station for four days.