There has been a remarkable improvement in capabilities for probing matter with x-rays and extreme ultraviolet (EUV) radiation since the previous edition of this book appeared in 2000. The spectral brightness and coherence of available research facilities has increased by many orders of magnitude across the EUV and x-ray spectral regions, extending from photon energies of 30 eV (40 nm wavelength) to 50 keV (0.25 Å). The ability to probe electron dynamics in atoms, molecules, clusters and solids has been extended from picoseconds to femtoseconds and attoseconds. X-ray optics have improved dramatically, with reflective and diffractive optics now able to focus, or resolve images, to 10 nm across much of this spectrum. New techniques have emerged for attosecond temporal measurements, nanoscale tomographic imaging of individual cells, and ever more sophisticated coherent diffraction and imaging techniques. Commercial capabilities have also improved with brighter laboratory sources and widely available x-ray microscopes for nanoscale imaging in the research and commercial sectors. And it appears that high-volume manufacturing of computer chips with 13.5 nm EUV radiation will soon become a reality, likely reaching world markets at the 7 nm node in 2017.