Now one such state, first proposed almost 50 years ago, has been created in experiments for the first time. Say hello to the supersolid, a state where atoms simultaneously exhibit a crystalline structure but still flow like a frictionless fluid.

The concept of a supersolid arose from the Nobel Prize-winning discovery in the 1970s of a superfluid, a liquid that has zero viscosity, meaning it flows with no resistance or "thickness." At the time, British physicist David Thouless theorized that a state of matter could exist where atoms are both free flowing like a superfluid, but also arranged in a crystalline structure, making it a supersolid.

Earlier attempts to produce this state used helium, the element that first exhibited superfluidity, but it was never brought to fruition. Now, two simultaneous – but independent – studies, one from ETH Zurich and one from MIT, have produced supersolids from Bose-Einstein condensates, using two different techniques.