Scientists have been given permission to genetically modify human embryos for the first time in the UK.
The Human Fertilisation and Embryology Authority (HFEA) regulator has approved a licence to use gene editing in research.
Scientists, who are searching for clues to what happens in the first seven days after fertilisation and want to investigate miscarriage, will not be able to implant the embryos into women.
A statement from the HFEA said: "Our Licence Committee has approved an application from Dr Kathy Niakan of the Francis Crick Institute to renew her laboratory's research licence to include gene editing of embryos.
"The committee has added a condition to the licence that no research using gene editing may take place until the research has received research ethics approval.
"As with all embryos used in research, it is illegal to transfer them to a woman for treatment."