A fuel cell stack having a plurality of fuel cells arranged adjacent one another and compressed together. At least one of the fuel cells has an electrode plate with a flow field formed therein, a proton exchange membrane and a compressible fluid-permeable diffusion media that is disposed adjacent the electrode plate. A compressing member is operable to vary a compression of the fuel cells during operation which varies an intrusion of the compressible diffusion media into the flow field in the adjacent electrode plate. The variation of the intrusion of the diffusion media into the flow fields allows the control of the pressure drop across the fuel cell stack and enables the fuel cell stack to be dynamically controlled so that a desired operational state is achieved.