This image shows the internal attachment mode of two electrons to a water cluster (average diameter of close to 2nm) comprised of 105 molecules. The shown configuration was obtained from first-principles quantum simulations. The wave function of the two excess electrons is depicted in pink and it is shown superimposed on the water molecules of the cluster. The compact dielectron distribution is localized in a hydration cavity in the interior of the cluster. The configuration shown here corresponds to the start of the dielectron hydrogen-evolution reaction. The protons of the two reacting neighboring water molecules, located approximately in the middle of the figure, are depicted by smaller blue spheres. Together with the dielectron these protons would form, in the course of the reaction, a hydrogen molecule. The oxygens and hydrogens of the water molecules are represented by red and gray spheres, respectively.