The new x-ray microscopes considerably improve on the resolution of optical microscopes. They can also be used to map the distribution of certain chemical elements. Some can form pictures in extremely short times, and some hold the promise of special capabilities such as three-dimensional imaging. Unlike conventional electron microscopy, x-ray microscopy enables specimens to be kept in air and in water, which means that biological samples can be studied under conditions similar to their natural state. The illumination used, so-called soft x rays in the wavelength range of 20 to 40 angstroms (an angstrom is one ten-billionth of a meter), is also sufficiently penetrating to image intact biological cells in many cases. Because of the wavelength of the x rays used, soft x-ray microscopes will never match the highest resolution possible with electron microscopes. Rather their special properties will make possible investigations that will complement those performed with light- and electron-based instruments.