Humans have been making metal alloys for thousands of years, and most of us can conjure a rough mental image of the process—it involves red-hot molten metals being mixed, poured, and shaped in a sweltering workshop or factory. This approach still works perfectly well for the traditional metals we see every day, like steel. But advanced metals with special chemical and mechanical properties, ones that scientists are investigating to use in energy technologies like long-lasting batteries and extreme-temperature engines for aerospace vehicles, need a more refined approach.