This handbook presents the development of synchrotron light sources and free-electron lasers as well as new scientific applications. Hardly any other discovery of the nineteenth century had such an impact on science and technology as Wilhelm Conrad R鰊tgen?s seminal discovery of X-rays in the year 1895. X-ray tubes soon became established as excellent instruments for numerous applications in medicine, biology, materials science and testing, chemistry and even public security. Developing new radiation sources with higher and higher brilliance and much extended spectral range for an ever widening field of research resulted in stunning developments like the electron storage ring and the free-electron laser. This second edition includes both updated chapters and new contributions highlighting the most recent developments in the field. Reports on operation experience of the new FEL facilities are complemented by discussions of new developments in X-ray beamline optics and detectors. Contributions on applications now include high pressure work, catalytic processes and engineering materials, medical applications and studies of cultural heritage. New contributions on IR spectroscopy, resonant inelastic X-ray scattering (RIXS) and studies of liquids complete this second edition.