If one end of a piece of metal is kept over fire, you probably don't want to hold the other end in your hand. This is because conductors of electricity also conduct heat. Yet, here, Dr. Alireza Nojeh reports on an unusual and counter-intuitive phenomenon called Heat Trap, whereby heat stays confined to a region of a conductor, without spreading to the surroundings. This effect was observed in carbon nanotubes forests (arrays of many many aligned carbon nanotubes forming a bulk structure) by his research group, and is an example of the unique and sometimes unexpected properties of nanomaterials. Heat Trap allows for extremely efficient and localized heating of these nanostructures, and enables us to create novel devices for applications in electronics, electron-beam technologies and clean energy conversion. For example, in this video, a solar thermionic convertor is shown: a device that generates electricity from sunlight based on the heating of a nanotube forest and emission of electrons through the thermionic mechanism.