The tip of a tunneling microscope hovers above a surface at a distance smaller than the diameter of an atom. Usually, it feels out the topography like a finger reading a page of Braille. Now, that same tip has learned to listen to how a membrane the size of a fingernail trembles.

In the new experiment, the microscope's tip became both a bow and a microphone. It gently touches the membrane with an electric field, making it vibrate, and then picks up those oscillations. At liquid helium temperatures, the membrane sings so clearly that its movements can be seen with picometer precision: that's a hundred times smaller than an atom.

This delicate approach neither heats nor slows the membrane. Previously, observing such vibrations required lasers or complex electrical circuits, which inevitably interfered. Now, you can peer into the private life of a microscopic oscillator without disturbing it.

This method opens the door to sensors that can detect forces thousands of times weaker than the weight of a dust mote. That means ultra-precise measurements of pressure and motion at ultra-low temperatures become possible — for instance, in the quantum devices of the future.