Quantum dots are manmade nanoparticles of semiconducting material comprising only a few thousand atoms. Because of the small number of atoms, a quantum dot's properties lie between those of single atoms or molecules and bulk material with a huge number of atoms. By changing the nanoparticles' size and shape, it is possible to fine-tune their electronic and optical properties—how electrons bond and move through the material, and how light is absorbed and emitted by it.