Multilayers can play a role in any situation where flux, rather than resolution, is desired. They are used in various classical optical arrangements ranging from double monochromators to grazing incidence mirrors. Beam focusing ca also be obtained by multilayer coating on a substrate that is either polished to a given shape, or dynamically bent, or grooved as a Bragg- Fresnel lens. With hard x rays, absorption plays a lesser role, allowing production of a very large bandpass through an aperiodic multilayer design, However, the sputtered, nanometer- thick individual layers are often amorphous, a cause of structural instability in case of a temperature rise. When the beam is intense, which is often the case with a synchrotron x-ray source, a number of solutions are envisaged, including efficient cooling, use of compound materials, and modification of the electric field distribution by nonperiodic arrangement. Results on the performance of multilayers and examples of applications are presented.