All matter can take 3 forms :solid , liquid , and gas. The difference is how fast the atoms or molecules move. The colder the temperature , the slower they move. And so hydrogen gas becomes a liquid at temperatures near absolute zero. Liquid hydrogen would be easier to transport and contain than the normal gas state of hydrogen if there was no requirement to maintain these extreme cold temperatures. Scientists are working on complex molecules which would approximate hydrogen in solution. See Science Codex. Then hydrogen could be used interchangeably with gasoline or diesel fuel. Then it would be simpler to store and transport. N1R needs continuing research into the possibilty of commercially converting hydrogen gas to a liquid state without refrigeration.