For decades, science has been trying to unlock the mysteries of how a single cell becomes a fully formed human being and what goes wrong to cause genetic diseases, miscarriages and infertility.
Now, scientists have created living entities in their labs that resemble human embryos; the results of two new experiments are the most complete such "model embryos" developed to date.
The goal of the experiments is to gain important insights into early human development and find new ways to prevent birth defects and miscarriages and treat fertility problems.
But the research, which was published in two separate papers Wednesday in the journal Nature Portfolio, raises sensitive moral and ethical concerns.
"I'm sure it makes anyone who is morally serious nervous when people start creating structures in a petri dish that are this close to being early human beings," says Dr. Daniel Sulmasy, a bioethicist at Georgetown University.
"They're not quite there yet, and so that's good. But the more they press the envelope, the more nervous I think anybody would get that people are trying to sort... see more