Magnetic nanoparticles (mNPs) ranging from the nanometre and micrometre scale have been widely applied in recent years in the area of biomedicine. They contain unique magnetic properties and due to their size can function at a cellular level, making them attractive candidates for cell labelling, imaging, tracking and as carriers. A recent surge of interest in nanotechnology has boosted the breadth and depth of the nanoparticle research field. This review aims to supplement a previously published review in 2003 and address more recent advances in the uses and bioapplications of mNPs and future interesting perspectives.