Scientists have created synthetic human embryos using stem cells in a groundbreaking advance that side-stepped the need for eggs or sperm. Scientists say that these model embryos – which resemble those in the earliest stages of human development – could provide a crucial window into the impact of genetic disorders and the biological causes of recurrent miscarriage. However, the work also raises serious ethical and legal issues as the lab-grown entities fall outside current legislation in the UK and most other countries. The structures do not have a beating heart or the beginnings of a brain, but include cells that...