This book provides a general overview of the various aspects of the properties, production, storage and application of hydrogen. Emphasis is placed on the thermodynamics of hydrogen as well as its application in vehicle technology and energy engineering. With reference to research projects at the Graz University of Technology and HyCentA, Hydrogen Center Austria, the current state of the art is presented in a well-founded manner. The sections on electrolysis for the production of hydrogen from green electricity and on fuel cells for the generation of electricity for electric drives in particular have been updated and supplemented.