Lab-grown models of embryos increasingly resemble the real thing

The traditional way to make an embryo is to combine a sperm cell with an egg, often after dinner and a bottle of wine. But a new way may be around the corner. In recent years scientists have discovered that they can persuade stem cells—those with the ability to transform into many other sorts of cells—to form structures that look and behave very much like embryos.

“Embryoids”, as such creations are called, can help with the study of embryology and pregnancy, and how they can go wrong. Some of the facsimiles look strikingly real. In 2022 two teams, one led by Magdalena Zernicka-Goetz, who works at the California Institute of Technology and the University of Cambridge, and another by Jacob Hanna at the Weizmann Institute of Science, in Israel, published papers describing mouse embryoids with rudimentary guts, brains and beating hearts. In June Dr Zernicka-Goetz published a paper describing a human embryoid designed to mimic the earliest stages of development, shortly after a real embryo would have implanted into its mother’s womb.