No one has ever seen dark matter, but it should pass through detectors like wind through leaves. Sometimes, very rarely, a dark matter particle bumps into an atomic nucleus, and then the detector must catch that jolt. The trouble is that light dark matter particles can hardly move heavy nuclei: it's like trying to knock down a bowling pin by throwing a feather at it. You need a target made of light nuclei, which are easier to shake.

Scientists took a trans-stilbene crystal — an organic material rich in hydrogen, the lightest nucleus. When a particle hits such a crystal, it flashes: a short pulse of light is born. This light was captured by two sensitive tubes pressed against the crystal's ends. The crystal, about the size of a pinky nail, roughly a centimeter in diameter and length, was irradiated with gamma rays from radioactive americium. A gamma quantum with an energy of 59.54 keV knocked out on average 3.37 light electrons per kiloelectronvolt of energy.

Such a bright and clear response shows that the crystal can distinguish weak events well and is suitable for hunting light dark matter. Now physicists have one more target that might catch those elusive particles.