Publisher Summary This chapter reviews the preparation and application of carbon nanotubes. Carbon nanotubes have caught the fancy of chemists, physicists, and material scientists. Interest, in this material has overshadowed that of fullerenes in recent years, although nanotubes still are not as readily available as fullerenes. The market price of nanotubes is still too high, and new synthesis methods based on a continuous process need to appear for this scenario to change. It should be noted that the laser method for producing SWNTs reported in 1996 provided a boost by making adequate quantities of pure SWNTs available. Many theoretical predictions were based on modeling SWNTs, and this availability of good quality SWNTs carried the possibility, for the first time, that some of these predictions could be tested. The most promising and fascinating developments have taken place in exploring the potential of nanotube electronics. Important concepts based on nanotube molecular devices have been demonstrated, but the biggest challenge still remains in building nanotube-based architectures to suit existing or future electronic fabrication technology. Nanotubes can be considered to be the ultimate carbon fiber, and it will be surprising if applications for nanotube are not developed in areas where traditional carbon fibers are abundantly used. One of the problems for nanotube-based composite is the lack of understanding of how the mechanics work around a nanosized inclusion or filler. With extremely small dimensions and mechanical strength, as well as elasticity, one area where nanotubes ultimately may become indispensable is their use as nanoprobes.