UK scientists have been granted permission by the fertility regulator to genetically modify human embryos under strict conditions. Researchers at the Francis Crick Institute in London hope that their gene-editing experiments will provide a deeper understanding of the earliest moments of human life and could provide insight into the problems that can cause miscarriage. The research, which will be led by Dr Kathy Niakan, will examine the first seven days after fertilisation, during which a single cell multiplies to around 250 cells.