For decades, researchers have known that the electron and its antiparticle, the positron, can join together to form a short-lived, hydrogenlike atom dubbed positronium. Now scientists at the University of California, Riverside, have managed to get two positronium atoms to stick together to form a molecule—di-positronium. The researchers first collected some 20 million positrons in an electromagnetic trap. They then fired the positrons in an intense nanosecond-long burst onto a microscopic spot on a thin, porous silica film. The positrons diffused into the pores, pulling in electrons and forming roughly 100,000 molecules of di-positronium. Investigating these molecules could open up new studies of antimatter and explain why so little of it exists in the universe. The gamma rays generated when electrons and positrons eventually collide might also be used to develop directed-energy weapons or to help ignite fusion reactions in nuclear power plants.

Make more sense of the matter in the September 13 Nature.