I am puzzled by Shuming Nie’s prognostication that quantum dots will “be the first example of nanotechnology that can really have some practical applications.” Colloidal gold particles of similar size to quantum dots have been used as high-resolution labels in electron microscopy for over 30 years. And due to their light-scattering properties, gold and silver nanoparticles have been used in stained glass since at least the 17th century!

Daryl A. Meyer
Madison, Wis.