Semiconductors are at the heart of most electronic devices that govern our daily lives. The proper functioning of semiconductor devices relies on their internally generated electric fields. Measuring these fields on the nanoscale is crucial for the development of next-generation electronics, but current techniques are restricted to measurements of the electric field at a semiconductor’s surface. Takayuki Iwasaki and a collaborative of researchers has reported a new method for sensing internal electric fields at the interior of operating semiconductor devices. The technique exploits the response of an artificially introduced single electron spin to variations in its surrounding electric field, and enabled the researchers to study a semiconductor diode subject to bias voltages of up to 150 V.