Ubiquitous Transformation: Electrical conversion can carry a big footprint, like this substation in the Sonoran Desert, in Arizona. It would be hard to overstate the importance of transformers in our electrical networks. They’re literally everywhere: on poles and pads, in substations and on private property, on the ground and under it. There are probably dozens in your neighborhood alone. It’s hard to imagine a world without them. But my colleagues and I are doing just that. In the distribution system, transformers typically take medium, or “primary,” voltages measured in the thousands of volts and convert them to secondary voltages—such as 120, 240, or 480 volts—that can be safely delivered to homes and businesses all over the world. It’s an approach that’s been used since before alternating current won the war of currents in 1892. It is difficult to name another electrotechnology that has survived as long. Nevertheless, it is time to start thinking beyond the conventional transformer. For one thing, transformers are bulky. They’re often cooled with oil, which can leak and is difficult to dispose of safely. Crucially, transformers are passive, one-way tools. They aren’t design...