Volume 41 of Reviews in Mineralogy and Geochemistry introduces to the field of high-temperature and high-pressure crystal chemistry, both as a guide to the dramatically improved techniques and as a summary of the voluminous crystal chemical literature on minerals at high temperature and pressure. The three parts of the book introduces crystal chemical considerations of special relevance to non-ambient crystallographic studies, reviews the temperature- and pressure-variation of structures in major mineral groups and presents experimental techniques for high-temperature and high-pressure studies of single crystals and polycrystalline samples as well as special considerations relating to diffractometry on samples at non-ambient conditions.