We now can see the cyclotron radiation from a single electron, folks!
The researchers plotted the detected radiation power as a function of time and frequency (Fig. 2). The bright, upward-angled streaks of radiation indicate the radiation emitted by a single electron. It is well known theoretically that a circling electron continuously emits radiation. As a result, it gradually loses energy and orbits at a rate that increases linearly in time. The detected radiation streaks have the same predicted linear dependence, which is what allowed the researchers to associate them with a single electron.
Of course, we have seen such effects for many electrons in synchrotron rings all over the world, but to not only see it for one electron, but to also see how it loses energy as it orbits around is rather neat. It reinforces the fact that we can't really imagine electrons "orbiting" around a nucleus in an atom in the classical way, because if they do, we would detect such cyclotron radiation and that they will eventually crash into the nucleus.
But I also find it interesting that this has more to do with the effort in trying to determine the mass of a neutrino independent of the neutrino mass oscillation via measuring the electrons mass to high accuracy in beta decay.