First image of a solid made of electrons

If the conditions are just right, some of the electrons inside a material will arrange themselves into a tidy honeycomb pattern — like a solid within a solid. Physicists have now for the first time directly imaged these ‘Wigner crystals’, named after theorist Eugene Wigner. Researchers built a device containing atom-thin layers of two semiconductors and cooled it to just a few degrees above absolute zero. This slowed the electrons between the two layers enough so that they formed the elusive material.