Indirect evidence of ‘dark photons’ has been spotted in the shrapnel of thousands of particle-smashing experiments. This could provide a glimpse into the mysterious nature of dark matter — which seems to make up most of the mass of the universe but is almost impossible to observe, other than by its gravitational effects. “The story is something like this: there could be an additional dark sector, where dark matter resides,” says particle physicist Carlos Wagner. Dark photons, if they exist, could weakly interact with normal matter, offering a window into the dark sector.