Carbon nanotubes were identified for the first time in 1991 by Sumio Iijima at the NEC Research Laboratory, using high resolution transmission electron microscopy, while studying the soot made from by-products obtained during the synthesis of fullerenes by the electric arc discharge method. In this soot, Iijima clearly observed the so-called multiwalled nanotubes, molecular carbon tubes with diameters in the nanometer range, consisting of carbon atoms arranged in a seamless graphitic structure rolled up to form concentric cylinders. Two years later, single-wall carbon nanotubes were synthesized by adding metal particles to the carbon electrodes
