After a human sperm and egg unite, a new embryo spends its first few weeks looking blobby. There’s no obvious top or bottom, and it is unclear which cells will give rise to which body parts. After about 14 days, the embryo elongates and forms layers, revealing a rough plan for the body. But this dramatic transformation, called gastrulation, has never been directly observed in human embryos: Growing them to this stage in a lab is technically difficult and ethically fraught. Now, researchers have made structures from human stem cells that mimic some features of embryos after gastrulation, an advance that could reveal how genetic mutations and chemical exposures can lead to miscarriages and birth defects.

Insoo Hyun, senior lecturer at the Harvard Medical School Center for Bioethics, and Jeantine Lunshof, lecturer at Harvard Medical School on behalf of the Harvard Center for Bioethics, weighed in on the ethical implications of this new development in a  June 11, 2020 news item in Science.

Read the full news item in Science here, or view an abstract of the study originally published in Nature here.