In the context of the energy transition, energy storage is a central technical, economic, and energy policy topic. The authors of this compact work provide a comprehensive overview of the various aspects of energy storage. They first describe the significance of energy storage in energy supply and define its role within it. Then, they address the storage needs in electricity, heat, and fuel supply in the context of the energy transition. The main part of the book presents various storage technologies in detail and discusses their advantages and disadvantages. Practical application examples and the integration of storage across all energy sectors complete the book. Numerous graphics and examples illustrate the entire field of energy storage and are available online in multiple languages and in color as a supplement. The 2nd edition includes.