Multilayer optics is one of the widely applied optics for conditioning an X-ray beam in the region of X-ray diffraction. Multilayer optics offers a well-balanced performance. The beam conditioned by a multilayer optic is characterized by low divergence, good spectrum purity, and high intensity. This article will start with a short historical note of the development of X-ray multilayer and a summary on the basic performance characteristics of X-ray multilayer, then move on to the discussion on the design principle of one- and two-dimensional optics. Both parallel beam optics and focusing optics will be addressed. As examples, selected applications of multilayer optics are also briefly discussed. Finally, the main problems associated with the application of multilayer optics are identified and the future developments are discussed.
