Researchers from the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI) have developed a new method to modify the spectral width of extreme-ultraviolet (XUV) light. By employing a novel phase-matching scheme in four-wave mixing, they could compress the spectral width of the initial broadband light by more than hundred times. The detailed experimental and theoretical results have been published in Nature Photonics.