Scientists at the University of Tokyo have captured something never seen before: a frame-by-frame view of how electron spins flip inside an antiferromagnet, a material once thought to be magnetically “invisible.” By firing ultrafast electrical pulses into a thin layer of manganese–tin and tracking the response with precisely timed flashes of light, the team uncovered two distinct switching mechanisms. One relies on heat generated by strong currents, while the other flips spins directly with minimal heating — a far more efficient process.