This book focuses on next-generation smart windows which can change their optical-physical properties by reflecting and/or transmitting incoming light radiation to attain comfortable indoor temperatures throughout the year. The book will address different techniques and materials used in smart windows in a simple way, including the basic principles, materials synthesis and thin film fabrication, optical and electrochemical characterization techniques followed in laboratories and in industry. The application-oriented perspective of the book will make it suitable to study solar energy conversion where research in nanomaterials can be extended to smart window applications.