Mesoscopic physics is a fast growing discipline with countless potential applications. Understanding the science of mesoscopic materials with unique physical and chemical properties is important for the design of nanodevices and materials with unique properties. Clusters as mesoscopic particles represent an intermediate state of matter between single atoms and solid material. This book deals with the properties of clusters in matrixes, on surfaces, and in vacuum. The formation and application of cluster-based materials is discussed. This book will appeal to physicists, chemists, materials researchers, and advanced students.