Boron nitride nanotubes are materials whose existence theorists predicted before they were synthesized in laboratories. The pictured image is a simulation of a single nanotube. This material has the intriguing property that the greatest density of conduction electrons is along the tube axis. Boron nitride nanotubes thus can ballistically conduct electrons down the center of the tube.

Marvin L. Cohen, University of California, Berkeley. Physics Today 59 (6), 48 (2006). 2006, American Institute of Physics.