The primary goal of nanotechnology is to achieve nanoscale materials and devices with atomic precision. Toward this goal, breakthroughs have recently been made in the solution-phase synthesis and applications of atomically precise nanoclusters. This book presents the exciting progress in this new research field. The chapters are contributed by leading experts of the field and cover the synthetic methods, atomic structures, electronic and optical properties, and catalytic applications of noble metal nanoclusters. Such new nanocluster materials offer exciting opportunities for chemists and physicists to understand the fundamental science of nanoclusters, especially the atomic-level structure-property correlation and design of new materials, as well as for developing a range of applications including catalysis, biomedicine, sensing, imaging, optics, and energy conversion. The book will be of interest to readers and researchers in nanotechnology, nanochemistry, catalysis, and computational chemistry, as well as practitioners in industry R&D for new materials. It is written to be accessible to undergraduate and graduate students and, therefore, is an excellent teaching material.