A novel reversible proton exchange membrane fuel cell system that is based upon micro-sized membrane and electrode assemblies is discussed. The resulting micro-fuel cell has a reduced size and mass due to an improved design of the bipolar plates and current collectors. Bipolar plates often contribute over 75% of the fuel cell stack mass and volume in traditional fuel cell and electrolyzer designs that results in power densities near 0.1 kW/kg and 0.1 kW/liter. The micro-sized membrane and electrodes allow us to minimize the size of the gas-channels that feed reactants to the electrodes. Physical Sciences Inc.’s (PSI) micro-design approach minimizes stack features resulting in power densities greater than 1 kW/liter and specific power densities greater than 1 kW/kg.