When cells are exposed to ionizing radiation, more destructive chain reactions may occur than previously thought. An international team led by researchers from the Max Planck Institute for Nuclear Physics in Heidelberg has for the first time observed intermolecular Coulombic decay in organic molecules. This is triggered by ionizing radiation such as from radioactivity or from space. The effect damages two neighboring molecules and ultimately leads to the breaking of bonds—like the ones in DNA and proteins. The finding not only improves the understanding of radiation damage but could also help in the search for more effective substances to support radiation therapy.