Polarons are induced by using a laser to excite Rydberg atoms contained as impurities in a Bose–Einstein condensate. In those Rydberg atoms, the average distance between the electron and its nucleus can be as large as several hundred nanometres, which is more than a thousand times the radius of a hydrogen atom. Under these circumstances, the distance between the nucleus and the electron of the excited Rydberg atoms is higher than the average distance between the atoms of the condensate. As a result, some atoms lie inside the orbit of the Rydberg atom's electron.