This book examines the development, use, extraction, and recovery of rare earth metals. Rare earth elements (REEs) occupy a key role in daily life in industrial applications. They are one of the critical elements for energy and sustainable growth. REEs are utilized in many modern electrical and electronic devices such as smart phones, computers, LED lights etc. Recovery of the REEs from secondary resources represents a way to meet the growing demand for electronic devices. Because of their rarity, utility, and importance, the recovery, utilization and recycling of rare earth metals is of utmost importance. This book presents both current methods of processing rare earths from primary and secondary sources and new, green routes for their isolation and purification. The book also addresses their utilization, re-use, reduction, and recycling policies that exist globally. Applications in metallurgy, magnets, ceramics, electronics, and chemical, optical, and nuclear technologies are discussed.