Precisely how chemical species interact in biochemical solutions or at the interface between solid and liquid is a question of great importance to chemists. Answers will provide insights at processes in catalysts, smart functional materials and even physiological processes in the body, which are essential for health. Now, researchers at Helmholtz Zentrum Berlin have developed a new black box tool that allows them to take the fingerprints of such interactions on the atomic scale. The team explains that the system builds on earlier, well replicated research using X-ray spectroscopy that reveals the disappearance of photons at some specific photon energy and correlates this with chemical interactions via a proposed a dark channel mechanism. Colleagues at the University of Rostock provided the theoretical underpinnings to make the link between high-resolution spectroscopic data and the mechanism.