Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtainthe best experience, we recommend you use a more up to date browser (or turn off compatibility mode inInternet Explorer). In the meantime, to ensure continued support, we are displaying the site without stylesand JavaScript.AdvertisementWhat’s next for lab-grown human embryos?You have full access to this article via your institution.It was day 13 in a set of experiments in Ali Brivanlou’s laboratory and he had an agonizing task ahead. His team of developmental biologists had thawed...…Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtainthe best experience, we recommend you use a more up to date browser (or turn off compatibility mode inInternet Explorer). In the meantime, to ensure continued support, we are displaying the site without stylesand JavaScript.AdvertisementWhat’s next for lab-grown human embryos?You have full access to this article via your institution.It was day 13 in a set of experiments in Ali Brivanlou’s laboratory and he had an agonizing task ahead. His team of developmental biologists had thawed...WW…