A modern fuel cell is usually made of a stack of individual cells that are mechanically pressed together. In MOD-FC the pressing takes place not mechanically but hydraulically. Due to the complete flushing of separate individual cells with the hydraulic medium, a homogeneous pressing of the inner cell components is ensured. In addition, the hydraulic medium can be directly used as a cooling medium. This ensures a homogeneous electric current generation among the surface and also that no life shortening hot spots appear. By the nearly ideal operating conditions MOD-FC are capable to examine in-situ membrane electrode units. First functional models are already in use (see figure). A plurality of simultaneously reproducible samples can be examined under the same operating conditions, which improve the quality of test results and reduces significantly the amount of sampling tests. Moreover, individual elements can be replaced by separate individual cells without great effort, due to the modular design of the stacks. In contrast to conventional fuel cell stacks MOD-FC can thus be maintained at a cellular basis.