Early human development is a complex, multistep process that’s even more complicated to study in the lab. Models made from stem cells avoid some of the trouble with using real human embryos.
In June, the possibility of synthetic embryos was announced at a conference. This allows some research to extend beyond the 14-day rule, which restricts experimentation on embryos beyond this period.
In April, scientists implanted synthetic monkey embryos in female monkeys. While none of them developed into fetuses, this is a new development that raises important ethical questions.