Some day we may be driving cars fueled by hydrogen. The hydrogen can be stored as a compressed gas, in liquid form, as a metal hydride, or by a chemical hydriding method. These cars may have an internal combustion engine, a fuel cell, or a combination of both. Some automobile manufacturers are targeting a pure fuel cell vehicle, while others are considering using fuel cells for auxiliary power and fueling internal combustion engines with hydrogen. In any case, the future of automobiles can be vastly different depending on the technological advancements of hydrogen storage and energy conversion.