This book provides a core foundation for understanding magnetic quantum-size effects at the nanoscale. It discusses physical, chemical, and nanotemplating synthesis techniques for the production of magnetic nanoparticles and covers experimental techniques for determination of the macroscopic and microscopic magnetization of nanoparticles. Other topics include magnetic ordering with increasing cluster size and transition from molecular to solid state. The book also discusses the role of nanomagnetism in high-density magnetic recording media, nanostructured permanent magnets, and geophysical and planetary science.