Chemical syntheses in liquids and gases take place in three-dimensional space. Random collisions between molecules have to result in something new in an extremely short time. But there is another way: on a gold surface under ultrahigh vacuum conditions, molecules lying still next to each other can be made to combine—even those that would never want to react with each other in a liquid. Researchers at Empa have now discovered such a reaction. Best of all, the experts can "take pictures" and watch every step of the reaction.