Molecular beam-scattering experiments have blossomed into a universal technique for understanding and controlling reactions in the gas phase and on solid surfaces. The Nathanson Group research confronts a third frontier: reactions at the surfaces of pure liquids, solutions, and monolayer films. They use gas-liquid scattering experiments to explore collisions and reactions of gas molecules with liquids ranging from crude oils and liquid metals to pure and salty glycerol, sulfuric acid, molten sodium hydroxide, and sodium carbonate.