Physicists get ultra-sharp glimpse of electrons

In this image showing the energy levels of electrons in a two-dimensional system, the electrons can be thought of as a sea, filling all the lowest places available and with a surface at sea level. In the picture, the dark line across the center is the sea level. Bright lines show where the energy levels are. The distance of the lines from the sea level shows how large their energy is, with lines below the center showing states that are normally filled (underwater) and lines above the center showing states that are normally empty (up in the air). Tracing out the energy levels as the number of electrons in the system is changed, from left to right in the plot, scientists can learn how electrons behave together in large groups. Graphic courtesy / Ashoori Group Lab