Fuel cells are advanced energy conversion and power generation systems with inherent high-energy conversion efficiency and environmentally-friendly operation. Fuel cells offer a realistic answer to the world's urgent need for pollution-free and efficient power. They represent an increasingly vital issue to engineers, the transportation industry and government. Fuel cells can achieve zero emission, and meeting the toughest emission standards; they are compatible with renewable energy sources and carriers with sustainable development. Due to their interdisciplinary nature, fuel cells involve and require knowledge of engineering thermodynamics, chemical thermodynamics, electrochemistry, mass transfer, heat transfer, fluid mechanics, manufacturing and design, engineering optimization, materials science and engineering, chemistry and chemical engineering, and electrical engineering.