This book describes the history of and recent developments in cobaltite and the spin-crossover (SC) phenomena. It offers readers an overview of essential research conducted on cobaltite and introduces them to the fundamentals of condensed matter physics research.The book consists of two parts. The first part reviews SC phenomena, covering the fundamental physics of SC phenomena and basic material properties of cobaltite. The second part focuses on recent topics in SC cobaltite, including the optical and dynamical features of cobaltite, thin material fabrication, and thermoelectric properties. The comprehensive coverage and clearly structured topics will especially appeal to newcomers to the field of state-of-the-art research on cobaltite and SC physics.