Clusters constitute a fascinating field of research in physics, chemistry, and materials science. This book introduces atomic clusters, ranging from the weakly bonded clusters of argon to strongly-bonded carbon clusters and metal nano-particles. It describes the experimental generation, detection, and interrogation of clusters along with theoretical approaches developed to help readers understand the physical properties. It classifies clusters according to their bonding types and gives examples of present and possible future applications of clusters in electronic, optical and magnetic devices.