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.