For the fuel cell to function, hydrogen is required at the anodes of the individual cells for oxidation. The anode subsystem is responsible for providing the hydrogen at the anode and contains all hydrogen-carrying components. It is thus the interface between the hydrogen storage system and the cell components of the anode. The system includes the important components for hydrogen injection and recirculation, as well as the valves and control technology. Much of the research and development work is concerned with optimizing these individual components, but the design and layout of the subsystem can also make an important contribution to minimizing parasitic losses and increasing the efficiency of the fuel cell.