This volume of Solid State Physics provides a broad review on recent advances in the field of magnetic insulators, ranging from new spin effects to thin film growth and high-frequency applications. It covers both theoretical and experimental progress. The topics include the use of magnetic insulators to produce and transfer spin currents, the excitation of spin waves in magnetic insulators by spin transfer torque, interplay between the spin and heat transports in magnetic insulator/normal metal heterostructures, nonlinear spin waves in thin films, development of high-quality...