X-ray machines have changed little over the century: a metal filament heated to 1,500 C in a glass vacuum tube shoots out electrons that hit a piece of metal, generating the radiation that travels through flesh but not bone. Physicist Otto Zhou at the University of North Carolina has come up with a cooler way to make x-rays. Zhou replaces the filament with carbon nanotubes-large, pipelike carbon molecules. Exposure to a weak electric field causes the nanotubes to emit electrons, which in turn produce x-rays the conventional way and make images such as the one shown. Because the whole process can take place at room temperature, there’s no need for heavy equipment to heat up the electron source. Nanotube-based x-ray machines can therefore be much smaller than conventional ones, making portable devices possible. To commercialize the technology, Zhou cofounded Applied Nanotechnologies in Chapel Hill, NC. The company aims to have its first product on the market within two years.