Researchers at the Francis Crick Institute in London have used CRISPR-Cas9 "to disrupt the production of a protein called OCT4 that is important for embryo development."

The first-of-its-kind study used 58 embryos donated by fertility clinics no longer needed for in-vitro fertilization. But now that they've started down the slippery slope of experimenting on humans, how far will scientists go?