NOVELTY - An electrochemical cassette comprises at least one membrane electrode assembly adapted for contact with at least two plates, each plate comprising flow field(s), each of which comprises groove(s). Each membrane electrode assembly and each plate comprise oxidant manifold opening(s) and fuel manifold opening(s). Each plate has sealant channel(s) which extends through at least a portion of its thickness.    USE - The electrochemical cassette such as fuel cell cassette, is useful in a fuel cell stack (claimed), e.g. proton exchange membrane fuel cell stacks.    ADVANTAGE - The cassette minimizes or prevents exposure of membrane electrode assemblies to reactants, waste streams, or cooling fluids around the various manifolds, thus avoiding cross-cell potential problems or material incompatibility. The fuel cell stack can be formed at reduced injection pressures to simplify component design and which do not require that a large area of each layer to be sacrificed to accommodate a sealing process. It can also be fabricated with a minimum of labor, reducing their cost and allowing for process automation.    DETAILED DESCRIPTION - An electrochemical cassette comprises at least one membrane electrode assembly adapted for contact with at least two plates, each plate comprising flow field(s), each of which comprises groove(s). The flow fields consist of oxidant flow field, fuel flow field, or coolant flow field. Each membrane electrode assembly and each plate comprise oxidant manifold opening(s) and fuel manifold opening(s) where each respective manifold opening extends through the thickness of the cassette. Each plate has sealant channel(s) which extends through at least a portion of its thickness. The membrane electrode assemblies and plates are assembled and encapsulated at its periphery by a sealant. The sealant contemporaneously seals the respective channels of the plates to selectively block those reactant manifold opening which are not intended to deliver material to a particular flow field.    An INDEPENDENT CLAIM is also included for a fuel cell stack comprising electrochemical cassette(s), and end plate(s) having opening(s) which align with the reactant manifold opening(s). The end plate is assembled on top and/or bottom of the stack of electrochemical cassette(s) such that the openings in the end plate align with the fuel manifold openings, the oxidant opening, and optionally the coolant manifold openings.    DESCRIPTION OF DRAWING(S) - The figure is a pictorial view of a fuel cell.