Quantum droplets are clumps of atoms cooled to near absolute zero. They form when magnetic atoms attract via dipole forces, but a constant microscopic jitter — quantum fluctuations — prevents them from collapsing. The droplet pulsates rhythmically, like a breathing ball. Its 'springiness' abruptly changes when transitioning from an ordinary Bose condensate (predicted by Einstein and Bose) to the droplet state. Chinese physicists developed a simple method to predict the frequency of this breathing: they used superposition — a mental blend of all motions — and derived concise formulas. Computer simulations and measurements of cloud expansion for dysprosium and erbium confirmed the calculations: the frequency jumped as if a foam ball turned into a rubber one. Thus, by measuring the droplet's pulse, one can precisely pinpoint the boundaries of the new phase and the strength of quantum jitter — just as Landau explained helium through collective waves. All of this became possible thanks to laser cooling to billionths of a degree. The method will pave the way to ultrasensitive sensors and the exploration of exotic states, such as supersolids.