Granted, it will be far too small for her to show off to her friends, but if your potential fiancée has a love of science, she just might accept this bauble over something flashier. It’s the world’s smallest diamond ring, created by a group of Australian physicists. The ring measures just 5 microns wide and 300 nanometers thick. And no, it’s not really for advertising your engagement. The ring is actually part of a device used to produce and detect single photons.

1. Einstein showed that light travels in bundles called quanta, which are at
the heart of the light-emitting diode. When electrons in a semiconductor-based diode move from one side to another, they shift to a less excited state, releasing energy in the form of photons. Channel these, and you get a bright, long-lasting light source.

2. In 1917 Einstein demonstrated that when a photon comes into contact with an atom, it can trigger a chain-reaction release of additional photons from