The global energy transition is not merely a substitution of fuels but a reconfiguration of the material, economic, and institutional foundations of modern civilisation. At its core lies a question that has animated this book: What is the realistic role of hydrogen in that reconfiguration? For decades, hydrogen has been portrayed alternately as a panacea for decarbonisation and as a distraction from more immediate solutions. The central problem addressed in this volume is how to distinguish between these two narratives—to separate the conditions under which hydrogen genuinely adds value from those where it merely recycles old expectations under new slogans.