This Special Issue of the Journal of X-Ray Optics and Instrumentation is devoted to a broad coverage of the increasingly important topic of X-ray focusing, including optics, beams, and applications. In part, this effort is a followup on a successful 2008 SPIE Optics and Photonics workshop on the same topic, with the goal of a comprehensive review of the topic in an archival form. Focused X-ray beams, ranging in size from nanometers to micrometers, are needed for a broad range of applications, from biology to material sciences, to interrogate physical, chemical, and biological states and processes with ever finer spatial resolution. In X-ray astronomy, improved focusing optical systems are needed for imaging faint or new objects. This Special Issue covers the latest in X-ray focusing techniques including theory, development, limitations, progress, and applications in a single archival document.

Topics to be covered in this Special Issue include, but are not limited to:

• Micro- and nanofocusing techniques (mirrors, multilayer, lenses, crystals, zone plates, polycapillaries, Kinoform arrays, multipore, etc.)
• Theory and computations
• Metrology
• Implementation (mounting, etc.)
• Feedback and control
• Applications

Before submission authors should carefully read over the journal's Author Guidelines, which are located at http://www.hindawi.com/journals/xroi/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/ according to the following timetable: