Lab-grown models of human brains are advancing rapidly. Can ethics keep pace?

Pacific Grove, California--Pop a few human stem cells into culture, provide the right molecular signals, and before long a mock cerebral cortex or a cerebellum knockoff could be floating in the medium. These neural, or brain, organoids, typically just a few millimeters across, are not "brains in a dish," as some journalists have described them. But they are becoming ever more sophisticated and true to life, capturing more of the brain's cellular and structural intricacy. "It's surprising how far this [area] has advanced in the last year," says John Evans, a sociologist at the University of California San Diego who follows the research and public opinions on it. That progress has allowed researchers to delve deeper into how the human brain develops, functions, and goes awry in diseases, but it has also sharpened ethical questions.