Hydrogen is the most abundant element in the universe. The dihydrogen molecule, with an H-H bond, is one of the simplest and most flexible in chemistry. Cleaving a dihydrogen bond to produce or store energy requires designing the catalyst with the perfect balance of properties to achieve the desired reactivity. In addition, the ability to get that molecule to reassemble itself and to control the rate of assembly and disassembly is important in the production of clean fuels. Morris Bullock and his colleagues at Pacific Northwest National Laboratory achieved control over the rate of cleavage and reassembly of a dihydrogen molecule.