Devices called spin valves have become crucial for magnetic sensing and data storage1, 2. They consist of two layers of ferromagnetic materials (which exhibit the familiar form of magnetism found in iron bar magnets), and have low electrical resistance when the direction of magnetization of the layers is the same, but high resistance when the magnetizations are antiparallel. Such devices can be switched between these states using a magnetic field or a large spin-polarized current — an electrical current in which the majority of electrons have the same spin orientation. On page 370 of this issue, Heron et al.3 report a method to control spin-valve states at room temperature using an electric field. Their approach consumes much less energy than using spin-polarized current, and opens up opportunities for miniaturizing spin valves that are not possible for magnetically controlled devices.