Several years of worldwide revolutionary developments in nanoscience, combining chemistry, physics, material science and biosciences have brought to another level of science. Nanotechnology & nanoscience integrate the better explanation and control of matter at dimensions of 1–100 nm, where unique physical, chemical and biological phenomena enable novel applications. Iron Oxide nanoparticles (MNPs) have been extensively studied both for their technological purpose and scientific work, due to its unique electrical, optical, superparamagnetic and spin dependent transport properties. Iron Oxide and substituted spinel ferrites have considerable important applications including magnetic fluids recording, catalysis, biotechnology/biomedicine, material sciences, photo catalysis, electrochemical, and bioeletrochemical sensing microwave absorption, magnetic resonance imaging etc. This is the first book in which boron doped Fe3O4 NPs were studied and their magneto-optical and electrical properties were investigated.