About 800 million children have blood lead levels that affect their brain. Guilarte has been among the first to document what's happening at the cellular level of the brain that triggers a cascade of lifelong consequences—from learning difficulties and lower IQ scores to the risk of psychiatric diseases and drug abuse in adulthood. Can the damage lead has done to their children ever be undone? Decades of research has brought Guilarte and his collaborators closer to an answer. They've identified a certain flavonoid, a class of nutrients present in fruits and vegetables, that reverses some of the negative effects of...