"By the time a fetus is 6 months old, it is producing electrical signals recognizable as brain waves. And clusters of lab-grown human brain cells known as organoids seem to follow a similar schedule, researchers reported Thursday in the journal Cell Stem Cell. "After these organoids are in that six-to-nine-months range, that's when [the electrical patterns] start to look a lot like what you'd see with a preterm infant," says Alysson Muotri, director of the stem cell program at the University of California, San Diego."