Book excerpt: Pressure, like temperature, is one of the most important parameters governing the state of matter. Today, high-pressure science and technology is applied to diverse research fields: physics, chemistry, biology, earth and marine sciences, material science and technology, chemical engineering, biotechnology and medicine. Research on liquids and solutions at high pressure is not only important for elucidating the structure of liquids, intermolecular interactions between solutes and solvents and chemical reactions in solutions, but also for providing fundamental numerical data for the design of chemical plants and the development of chemical processes. In particular, high-pressure studies of water and aqueous solutions are closely correlated with research into bioscience and biotechnology. In this volume some of the most important and most recent advances in liquids and solutions at high pressure in Japan are presented.