Geoff: How did you know? I directly worked with quantum dots, or, semi-conductor nanocrystals, for several years in a variety of biological applications for the biotech industry. They are composed of a crystaline core and a shell of a few thousand atoms (as an insulator to protect the core from oxidative damage) and usually are about 5 to 10 nm in diameter. They are not easy to make as a bulk with a uniform, small-size distribution. But excite them with a voltage or by laser photonic energy, and they emit a bright beautiful band of fluorescence color that is highly photostable.