Abstract: This edited book, which is a piece of artwork prepared TUBA-Energy Working Group, brings a holistic approach to energy and covers all aspects of it, ranging from its history and importance to fundamental thermodynamic concepts and from the dimensions of energy systems to the role of innovation in these systems. The topics covered in the book are extensive and include basic thermodynamic concepts and methods, traditional fossil fuels, renewable energy resources, nuclear energy, biofuels, and alternative fuels, hydrogen energy, waste-to-energy, energy conservation and efficiency, energy storage, energy materials, smart grids, energy policies and strategies, economics and effectiveness of energy systems, energy- environment-sustainability as well as energy innovation.