In nanomedicine, iron oxide nanoparticles are at an advanced stage, being commercialized for cancer treatment and iron-deficiency anemia treatment. Their therapeutic efficacy comes from their ability to target a tissue, activate a drug, locally produce a temperature increase following (or not) the application of an external source of energy, modify genes or activate various biological materials, or replace diseased cells by stem cells. Owing to these various mechanisms of action, they can potentially be used for treating a whole range of different diseases, making them more appealing than conventional drugs that target a more limited number of indications.