Magnetoencephalography (MEG) is a powerful technique for mapping brain activity in real time. Current MEG scanners are cumbersome and require subjects to remain motionless during the procedure, which limits its use. Now, a MEG system has been developed that uses quantum sensors mounted in a lightweight helmet that also cancels the Earth's magnetic field, which would otherwise interfere with readings. The new technology can record MEG data at millisecond resolution in moving subjects and has the potential to dramatically expand the application of MEG.