Electrons in aqueous solution, also known as hydrated electrons, can be formed by ionizing radiation in cells and are of interest for their role in free-radical formation and DNA damage. Now, five decades after their original discovery, researchers have finally found a way to determine fundamental properties of such electrons, reports a group led by Bernd Abel of Leipzig University, in Germany (Nat. Chem., DOI: 10.1038/nchem.580). The researchers generated solutions with solvated electrons by using an ultraviolet laser pulse and then studied the solutions using ultrafast liquid-jet photoelectron spectroscopy. They found that the energy to eject a hydrated electron from bulk liquid water into a vacuum, or the electron’s vertical binding energy (VBE), is 3.3 eV. The VBE of an electron at a water surface is 1.6 eV. Both values are similar to those estimated from studies of water cluster anions. The researchers hypothesize that solvated electrons at interfaces, such as hydrophilic-hydrophobic regions of cells or proteins, may be key to understanding the role of the species in breaking chemical bonds.