Improvements in vacuum deposition technology have made it possible to produce structures in whichotwo materials are arranged in alternating layers of uniform thickness. These layers may be as thin as 5A. Such structures act as Bragg diffractors or "artificial crystals" for x-rays - alternatively they may be viewed as multilayer interference coatings. These devices have many potential applications in x-ray and euv astronomy. Through the use of a dynamical theory, we show how the properties of LSM's depend on the layer materials and thicknesses and how these properties may be "tailored" for specific applications. Laboratory results at various x-ray wavelengths are presented. Finally, specific x-ray astronomy applications in the areas of spectroscopy, imaging, polarimetry and laboratory calibration are discussed.