We might think that nanotechnology, like the use of quantum dots, is a recent development. Not so. When I was working on my qualifying exam for grad school, I chose the topic of light scattering from a medium containing “inclusions” of foreign material. One of the examples given in the literature was the use of gold and silver in glass objects made by Romans two millennia ago. Somehow, they had hit on a formula that left nanosized particles of these metals inside the glass. Because of the way electrons were able to move (almost) freely inside the particles, they can interact strongly with light of visible wavelengths during a phenomenon called “plasmon resonance.” Here is an interesting example of the technology, the Lycurgus cup, which is now in the British Museum.