Magnetic nanoparticles have been fabricated by wet-chemical routes, such as thermal decomposition and hydrothermal process. Apart of spherical Fe3O4 nanoparticles, we have also fabricated Fe3O4 naorings and nanodiscs. Because of vortex domain structure, magnetic nanorings and nanodiscs can be relatively well suspended, even if their sizes are much larger than the critical size for superparamagnetism. These nanorings and nanodiscs possess relatively large magnetic hysteresis loss, which could result in excellent performance for magnetic hyperthermia. We have performed in-vivo hyperthermia. The results demonstrate that magnetic nanorings are promising hyperthermia agent for cancer treatment. Fe3O4 nanodiscs could be aligned under magnetic field. This has resulted in a great enhancement of magnetic hyperthermia performance. In addition, these magnetic nanoparticles have shown excellent results for MRI contrast enhancement. In this work, we have also fabricated Fe3O4 films by wet-chemical process. These films have shown enhanced magnetization.