This book explores the range and the utility of supercritical fluid system in a variety of diverse chemical applications. The book highlighted the green process and served the necessary background and details about separation, material processing, and reaction regarding technique, mechanism, protocol, and potential applications; hence it can appeal to academics and industrialists. Both from a chemical as well as engineering scene, the book updates the recent advances in supercritical fluid technology and other pressurized-solvent system (subcritical water technology). The most wide-spread use of supercritical CO2 as a solvent has been in supercritical fluid extraction and fractionation processes. Other applications are recrystallization of pharmaceuticals, metal nanoparticles generation, and polymer processing. Sub or supercritical water is a unique green solvent which can serve a high solubility for many weakly-polar organics and light inorganic gases. This solvent denotes very high reactivity for biomass processing.