In much of the world, sustainability is the order of the day. But what exactly does the term mean? The basic idea is dealing with energy and raw materials more carefully and with greater forethought than people often have in the past. For example, it means not letting plastic waste get out of hand, even though the material makes our lives easier. Or how hydrogen can be produced on an industrial scale in an environmentally sound way. Sustainability ought to show societies and companies the path to a livable future.