The Rayleigh-Taylor instability is a fluid phenomenon that occurs across all scales, from filament growth in supernovae, to hindering the efficiency of energy extraction from some forms of fusion, but you'll most likely have only come across it when adding milk to coffee. In essence, when a heavy fluid rests atop a lighter one, it is unstable. The top fluid sinks while the bottom rises. They get around ecah other through the growth of a surface wave, that develops into plumes. This is difficult to set-up reproducibly as the fluids want to switch places well before you've got a nice two-layer system. We got around this problem using magnets, and set the experiment up so the top layer is lighter (and so doesn't sink), but is also more attracted to the magnet that the chamber is descending towards. We then showed that rotating the chamber slows - but does not halt - the growth of this magnetically induced instability. Whether this is a useful result is for the theorists to work out, I just did the experiment!