Carbon nanotubes are a relatively new allotrope of carbon. They consist of carbon atoms bonded into a tube shape, sometimes as single-wall carbon nanotubes, and sometimes as multi-wall carbon nanotubes. Although they 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 their discovery.
Carbon nanotubes have many remarkable properties that scientists are only just starting to exploit. First of all, they are extremely strong, probably one of the strongest materials that is even theoretically possible. Although the tubes 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 centimeters in length, research is ongoing to make them longer, and when "carbon nanotube rope" hits the market, it will be the strongest fiber available. The fiber is so strong that it is 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, they 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. Their use will allow the computing industry to create computers more powerful than those that 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.