^1st Fuel Cell: 1839. wow. William Grove broke down water into
   hydrogen and oxygen with electricity (and platinum and sulfuric
   acid) and was surprised to find that, when he reversed the
   process, the hydrogen and oxygen gases not only turned back into
   water, but generated ELECTRICITY. THAT'S why fuel cells are such
   a hot area of research (making it cheaply, efficiently, etc).
   They were used on Apollo missions and generated drinkable water
   for the astronauts while also powering the craft. Now I 'get
   it'.^