Composites of polymers and inorganic nanoparticles offer tremendous promise for the optimization of mechanical properties. Although many claims of improved properties and balanced optimization can be found in the scientific literature over the past several decades, very little fundamental insight has been provided for the true "nano" effect on mechanical properties. Crosby and Emrick have used a model polymer, linear polystyrene, and CdSe nanoparticles covered with a short polystyrene coating to isolate the fundamental mechanisms leading to enhanced failure properties in these materials. Clear evidence for the local rearrangement of nanoparticle fillers during the application of mechanical strain was discovered. This enhanced mobility on the nanoscale leads to a "self-assembled" microstructure that is more resistant to fracture.