In 1959, Richard P. Feynman gave a famous talk entitled “There’s Plenty of Room at the Bottom” in a meeting of American Physical Society conducted at Caltech, USA. Feynman discussed his vision, building of objects atom by atom or molecule by molecule. This was the first idea and constitution of “nanotechnology”. Hereafter, nanotechnology has been attracted considerable interests in materials science, which is driven by the expectations concerning the application of nanomaterials in many technological applications as a forthcoming generation of functional materials for the new century. Within the last decade, nanoscience and nanotechnology have been considered as the leading research area in the physical and life sciences and engineering. This book consists of synthesis and characterization of coated magnetic spinel nanoparticles by various solution-based processes including hydrothermal, surfactant-assisted, sonochemical, gel-to crystalline, thermal decomposition and co-precipitation methods. Structural, morphological, spectroscopic, magnetic and electrical properties of the spinel nanoparticles were characterized by XRD, FTIR, TEM, SEM, EPR, TGA, and conductivity measurements.