Scientists in Japan have successfully generated mice with two biological fathers by creating eggs from male cells, bringing us one step closer to making the film Junior a reality.

Scientists had previously generated mice with two fathers, but the process involved several complex stages, including genetic engineering. This is the first time that viable eggs have been made from male cells. According to The Guardian, this is a “major advance” that “opens up dramatic new possibilities for reproduction.” Wednesday in London, Japan’s Kyushu University’s Katsuhiko Hayashi presented the findings at the Third International Conference on Human Genome Editing. Hayashi projected that the procedure might be repeated in humans within a decade. However, others have argued that this timescale is unreasonable given that viable, lab-grown human eggs from female cells, let alone male cells, have not yet been developed.