This collection of original articles and surveys treats the linear and nonlinear aspects of the theory of partial differential equations. Original articles are self-contained with full proofs; survey articles give a quick and direct introduction to selected topics evolving at a fast pace. Phase space analysis methods, including microlocal analysis, have yielded striking results in past years and have become one of the main tools of investigation. Equally important is their role in many applications to physics, for example, in quantum and spectral theories. Graduate students at various levels as well as researchers in PDEs and related fields will find this an excellent resource.