Researchers from the ETH Zurich Department of Physics have developed the first high-​repetition-rate laser source that generates coherent soft x-​rays crossing the complete ‘water window’. The laser arrangement used in the demonstration generally works in the intense ultraviolet spectral band. Researchers have long been trying to achieve higher photon energies. Especially, in the water window occupied by soft x-rays radiation with wavelengths within 2.2 and 4.4 nm. This technological breakthrough opens up a wide spectrum of new opportunities. Coherent laser system in the water-​window spectral region, highly relevant for studies in chemistry and biology, and material sciences as well as in physics.