A team of researchers in the United States and United Kingdom say they have created the world’s first synthetic human embryo-like structures from stem cells, bypassing the need for eggs and sperm.

These embryo-like structures are at the very earliest stages of human development: They don’t have a beating heart or a brain, for example. But scientists say they could one day help advance the understanding of genetic diseases or the causes of miscarriages.

The research raises critical legal and ethical questions, and many countries, including the US, don’t have laws governing the creation or treatment of synthetic embryos.

The pace of discoveries in this field and the growing sophistication of these models have alarmed bioethics experts as they push ever closer to the edge of life.

“Unlike human embryos arising from in vitro fertilization (IVF), where there is an established legal framework, there are currently no clear […]