A term used to describe a technique and an instrument or combination of instruments which utilize x-radiation for chemical analysis and for magnification of 100–1000 diameters. The resolution possible is about 0.25 micrometer. X-ray microscopy is a relatively recent development among the microscopic techniques. The contrast in the x-ray microscopic image is caused by varying x-ray attenuation in the specimen. The advantage of x-ray microscopy is that it yields quantitative chemical information, besides structural information, about objects, including those which are opaque to light. It is a reliable ultramicrochemical analytical technique by which amounts of elements and weights of samples as small as 10⁻¹² to 10⁻¹⁴ g can be analyzed with an error of only a few percent.