Pressure-temperature time (P-T-t) paths are currently one of the most active areas of research in structural geology, petrology, and geochemistry. P-T-t paths can potentially reveal how different parts of mountain belts are spatially assembled and the time scale on which the assemby occurs. This book is intended as a primer on moder techniques of establishing the pressure-temperature evolution of metamorphic rocks through time. As such, it would be multidisciplinary.