In 2017, two research groups from ETH Zurich and from MIT reported on the creation of an ultracold quantum gas with supersolid properties. The Zurich group placed a Bose–Einstein condensate inside two optical resonators, which enhanced the atomic interactions until they started to spontaneously crystallize and form a solid that maintains the inherent superfluidity of Bose–Einstein condensates. This setting realises a special form of a supersolid, the so-called lattice supersolid, where atoms are pinned to the sites of an externally imposed lattice structure. The MIT group exposed a Bose–Einstein condensate in a double-well potential to light beams that created an effective spin–orbit coupling. The interference between the atoms on the two spin–orbit coupled lattice sites gave rise to a characteristic density modulation.