New research proposes that chondrules, small glassy beads that make up the bulk of the most primitive meteorites, played a crucial role in the formation of planets. Simulations developed by scientists at the American Museum of Natural History, Lund University in Sweden, and collaborating institutions show how asteroid-sized planetesimals—the building blocks of planets—can grow to observed sizes by sweeping up chondrules, each only about the size of a grain of sand. The work is published today in the journal Science Advances.