 Superparamagnetic iron oxide nanoparticles, SBIONs, have been used in many biomedical applications due to their ability to facilitate both diagnostic and therapeutic goals. However, complex interactions between these particles and cells can lead to toxic effects which may limit their clinical applications. This review paper examines the existing literature and compares the potential toxicity of SBIONs with similar surface chemistries on different cell types. The focus is on the cellular and molecular mechanisms behind the toxicity of SBIONs. Additionally, the toxicity of SBIONs in various cell lines, in vitro and animal models, as well as in vivo, is discussed. This article was authored by Rogaea Vakiligartovall, Amir Abbas Montazaborogini, Zainab Vakiligartovall and others.