The prospects for the role of hydrogen in the energy mix are rising, but not for the first time. To finally break through into the mainstream energy sector, the industry needs to scale up and reduce costs. As the use of hydrogen grows, it will also need to win both wider public acceptance and the right policy support. Hydrogen’s advantage is its versatility. In which applications can it best succeed? Where are the next technology and cost breakthroughs likely to come from? How can policy best support the hydrogen economy?