Chemists from 8 different chemical institutions have joined forces to bring you this new recipe for magnetic nanorings (Jia et al. 2008 DOI). Dimensions: height 80 -120 nanometer , outer diameter 150 nm and inner diameter 70 nm and each one made out of a single-crystal piece of iron oxide. As often in this brand of nanotechnology you can do the chemistry in the kitchen sink. Chemical analysis on the other hand takes a battery of rather expensive equipment.