Iron (II,III) oxide nanoparticles in their magnetite crystal form are the most explored magnetic nanoparticles. Magnetite nanoparticles possess strong ferrimagnetic behavior, enabling remote manipulation with external magnetic fields and straightforward separation from liquid media. Their magnetic losses under alternating fields also make them suitable for thermal conversion. Applications include data storage and RAM materials, magnetic separation of pollutants, MRI contrast enhancement, targeted drug delivery, and magnetic hyperthermia for cancer treatment.