 Superparamagnetic iron oxide nanoparticles, spiens, are a type of nanomaterial with unique properties which make them ideal for use in MRI and magnetic hypothermia. They can be easily synthesized, are biocompatible, and can be modified with different chemical agents. These properties make them highly attractive for use in oncology, especially in the treatment of brain, breast, prostate, and pancreatic tumors. Despite some drawbacks, such as their tendency to accumulate in macrophages, spiens show great promise in the field of medicine. This article was authored by Joanna Dylinskolajduka, Agnieszka Lazarczyk, Przemysław Halubiek, and others.