On Thursday, a group of notable scientists, including Nobel Prize winners and global health experts, issued a warning against researchers synthesizing a type of artificial cell that could rampage through life on Earth with practically no barriers to stop it. “Mirror cells,” as they are known, could one day compose “mirror life,” a type of synthetic organism that, on the molecular level, is the complete reverse of the life forms we know. But the 38 co-authors of the warning article published in the journal Science recommend that research into mirror life be blocked immediately, before it spirals out of control.