Fabrication of future generations of advanced film-based devices will require monitoring of ultrathin layers with sharp interfaces in which the layer thickness may reach atomic dimensions. It therefore becomes increasingly more important to be able to monitor film-deposition processes in situ and in real time under different background pressure conditions. Diffusion or surface segregation processes relevant to device fabrication also need to be characterized. To these ends, a variety of complimentary in situ, real-time characterization techniques are needed to advance the science and technology of thin films and interfaces. This book offers an interdisciplinary exchange of ideas from researchers with cross-disciplinary expertise. The application of in situ characterization methods are discussed in relation to different materials including oxides, nitrides, semiconductors, and metals analyzed at the macroscopic, microscopic and nanoscale level.