Magnetic iron oxide nanoparticles of 5-15 nm diameter behave as single domain superparamagnetic materials. Once these particles are coated with a surfactant layer and stably suspended in a liquid carrier, they form a suspension that is called a ferrofluid. This fluid exhibits magnetic behavior in the presence of an external magnetic field. Alternately, the nanoparticles can be embedded within solid materials, e.g., inside 1-2 μm size polystyrene microspheres.  In this case, the beads respond to external magnetic fields. Thus, magnetic fields offer a means to control the transport of ferrofluids and magnetic microspheres resulting in interesting applications. The particles can be coated with chemical substances and bioconjugates that impart them with the ability to conduct valuable functions. This combination of (bio)chemical functionalization and the “action-at-a-distance” using the magnetic field has considerable potential for applications of superparamagnetic nanoparticles in MEMS and NEMS (and BioMEMS and BioNEMS) devices. Examples include enhanced heat transfer, controlled mass transfer, and field-assisted self assemblies. The particles can be employed for microscale bio-assays or in vivo applications. Here, I discuss the contents of the paper "Field-Assisted Self-Assembly of Superparamagnetic Nanoparticles for Biomedical, MEMS and BioMEMS Applications" by R. Ganguly and I. K. Puri that appeared in Advances in Applied Mechanics (Vol. 41, 2007).