Researchers at the University of Michigan's Center for Ultrafast Optical Sciences in Ann Arbor have built a tabletop laser that generates a coherent x-ray beam. The scientists shot a rapidly pulsing laser through a hollow glass tube filled with gas. By controlling the pressure of the gas, the team generated a focused beam of x-rays that could be incorporated into an instrument that performs atomic-scale imaging. The advance could lead to applications in biomedicine, such as providing chemists with a close-up view of how atoms react with other atoms in cells. Although others have fabricated x-ray lasers, the Michigan scientists say their laser emits at a very short wavelength -- as short as 2 nm. The shorter the laser's wavelength, the higher the spatial resolution of the beam. Unlike traditional lasers, the x-ray laser has a short pulse duration that enables high temporal resolution imaging.