Scientists have produced Fe3O4 nanowires on 10-nm length scales by deposition on an MgO substrate. When cooled to 110 K, the nanowires showed a sharp Verwey transition — greater resistivity resulting from a change in crystal structure. This switching is essential for nanoelectronics, but hard to achieve in Fe3O4 nanowires. It was possible because of the low density of antiphase boundary defects, and will promote advances in green electronic technologies.