Prof. Xiyun Yan's group reported that magnetite nanoparticles possess an intrinsic enzyme mimetic activity similar to natural peroxidases. Based on these novel findings they developed a novel immunoassay using the multi-functions of antibody-modified nanoparticles (targeting, separation and catalysis). A commentary article in the same issue of Nature Nanotechnology noted that Yan, Perrett, and colleagues showed for the first time that iron oxide nanoparticles can function as peroxidase nanomimetics. Although the wide potential applications of this peroxidase-like activity of iron oxide nanoparticles in medicine and biotechnology remain to be explored, the "ready-made" simplicity of catalytic activity in iron oxide nanoparticles will certainly attract a lot of attention.