Charged particles in aqueous solutions are always surrounded by a shell of water molecules. However, much is still unknown about the nature of this so-called hydration shell. Using terahertz spectroscopy, chemists from Bochum have gained new insights into how an ion affects the water molecules in its environment. Prof Dr. Martina Havenith, Dr. Gerhard Schwaab and Dr. Federico Sebastiani from the Chair of Physical Chemistry II of Ruhr-Universität Bochum (RUB) provide an overview of the results of the experiments in the journal Angewandte Chemie in July 2018.