The European Theoretical Spectroscopy Facility (ETSF) is a center for knowledge on spectroscopy, which gathers together the experience and expertise of over 200 researchers from Europe and the United States. Spectroscopy is a technique used to determine the composition of a light source by breaking it down into its individual components, just like how raindrops refract sunlight in a rainbow. The center conducts cutting-edge research on theoretical and computational methods to understand and predict the spectroscopic properties of materials, which in turn, allows researchers to develop better materials for solar panels or optimize the transfer of an electrical current.