This book focuses on chemical reactions and processing under extreme conditions―how materials react with highly concentrated active species and/or in a very confined high-temperature and high-pressure volume. Those ultimate reaction environments created by a focused laser beam, discharges, ion bombardments, or microwaves provide characteristic nano- and submicron-sized products and functional nanostructures. The book explores the chemistry and processing of metals and non-metals as well as molecules that are strongly dependent on the energy deposition processes and character of the materials. Descriptions of a wide range of topics are given from the perspective of a variety of research methodologies, material preparations, and applications. The reader is led to consider and review how a high-energy source interacts with materials, and what the key factors are that determine the quality and quantity of nanoproducts and nano-processing.