Nature, Published online: 25 February 2026; doi:10.1038/d41586-026-00580-2

Current X-ray lasers require facilities that are kilometres long. A cavity-based set-up about 66 metres in length has been developed that uses highly reflective mirrors to enable the generation of high-intensity pulses of narrow-band X-ray radiation. This promises to overcome the limitations of current X-ray lasers.