Belousov–ZhabotinskyA chemical clock: a dish of liquid that flips colour back and forth instead of settling. Each spot fires, then needs to rest before it can fire again, so a nudge spreads as a travelling wave — and the waves wrap into endlessly turning spirals and target rings.Boris Belousov found the oscillation in 1951 while mimicking metabolism; every journal rejected it as impossible — chemistry was “supposed to” run downhill to equilibrium. Anatol Zhabotinsky confirmed it in the 1960s. It is now the textbook case of a system held far from equilibrium organising itself in space and time.