As recently as three years ago, clean hydrogen energy was on the fringes of the energy-transition conversation – an outlier solution, at least for the short or medium term. Today, it is rapidly moving into the mainstream and, for many, it is essential to a net-zero energy future. In short, the world is heading for hydrogen, but the route is uncertain and many questions remain. How quickly can hydrogen supply scale-up to support high-demand industries? What is new about hydrogen in 2021? What are the most urgent challenges and the required enablers? Which areas of uncertainty could impact hydrogen the most in the next few years?