Scientists have succeeded in growing human embryos in a lab for nearly two weeks.
It is the first time they have been grown beyond the stage where they would naturally implant themselves in a mother's womb.
It raises new ethical questions - including whether the 14 day legal limit on growing embryos should change.
IVF consultant Professor Geeta Nargund has said it is a big development: “This is an important scientific breakthrough.
“Implantation failure is a very common reason for failure of IVF as well for early miscarriages.”