Researchers who study developing human embryos have long limited their experimentation to lab embryos that are no more than 14 days into development. Some scientists are now pushing that boundary.
Ali Brivanlou slides open a glass door at the Rockefeller University in New York to show off his latest experiments probing the mysteries of the human embryo.
"As you can see, all my lab is glass — just to make sure there is nothing that happens in some dark rooms that gives people some weird ideas," says Brivanlou, perhaps only half joking.
