Friendships matter, for better or worse. Having friends improves happiness and health; but friendship networks also divide people because humans mostly befriend others that are just like them. A multinational U.S-European research team has conducted the largest-ever experiment to test how small environmental changes can shape friendship networks. The team randomized the seating charts within 182 classrooms, involving N=2,996 students. The researchers found that merely sitting next to each other in school greatly increased students' probability of becoming best friends. Importantly, the researchers found that sitting next to each other increased friendship potential for all children, regardless of their gender, class, or ethnic background. This demonstrates that simple ('light-touch") interventions can effectively diversify friendship networks. The findings of the study were published in the open-access journal 'PLOS ONE'.