 GammaFa203, Magamite, Fe3O4, Magnetite, and FeO, Wustite, are iron oxide compounds with unique properties at the nanoscale, making them ideal for surface functionalization and modification in various applications such as separation techniques, magnetic sorting, drug delivery, cancer hyperthermia, sensing, and increased surface area to volume ratio. An ideal synthesis method should control temperature, pH, stirring rate, particle distribution, size, shape, composition, crystallinity, purity, and rapid screening for reliable reproducibility. Different synthesis routes, mechanisms, characterization techniques, and applications of iron oxide nanoparticles, IONPs, are reviewed in detail. This article was authored by Nene Ajinkya, Cfangu, Poonam Kethil, and others.