Carbon nanotubes are a relatively new allotrope of carbon that was synthesized as early as 1952 or before. They consist of carbon atoms bonded into a tube shape, sometimes with a single wall — called single-wall carbon nanotubes or SWCN — or multiple walls — called multi-wall carbon nanotubes. Although carbon nanotubes have likely been synthesized in small quantities and observed since the invention of the transmission electron microscope in 1938, their present-day popularity follows from a paper published by Japanese physicist Sumio Iijima in 1991. Much of modern-day literature on the topic erroneously credits Iijima with the discovery of carbon nanotubes.

Nanotubes are considered a part of the fullerene family, of which buckyballs are another members. While nanotubes are carbon atoms in the shape of a cylinder, buckyballs are arranged into a ball.

Carbon nanotubes have many remarkable properties which we are only just starting to exploit. First of all, carbon nanotubes are extremely strong, probably one of the strongest materials that is even theoretically possible. Although nanotubes are only about a nanometer wide, they can be very long in comparison to their width, a useful property for strength.

Although the longest nanotubes that have been synthesized today are only a few cm in length, research is ongoing to make them longer, and when "carbon nanotube rope" hits the market, it will be the strongest fiber available. Carbon nanotube fiber is so strong that they are the only fiber that could be spun into a space elevator (a sky bridge connecting a counterweight in geosynchronous orbit to a position on the ground) without snapping. Recently, carbon nanotubes have been proposed as a building material for armor so strong that bullets bounce right off it.

Single-walled carbon nanotubes are excellent conductors, and many computing companies are developing ways to use them in computers. The use of carbon nanotubes will allow the computing industry to create computers more powerful than those which can be fabricated via the conventional method of photolithography.

Carbon nanotubes are capable of ballistic electron transport, meaning they are excellent conductors in the direction of the tube. This led them to be proposed as the ideal building material for the next generation of televisions, although the improvements of LCDs, including OLCDs, makes this unlikely in the near-term future.