Carbon nanotubes are tiny tubes made up of only carbon atoms and have diameters that are only a few nanometers wide. Even though they are so tiny, they are super strong. The reason that they are so strong is because of the way their carbon atoms are bonded together in the nanotube structure.
Diamonds are also made of only carbon atoms but have their atoms bonded in a different way so even though diamond is usually known as being the strongest material in the world, carbon nanotubes are actually stronger. If you look at a model of a carbon nanotubes you can see that every carbon atoms is connected to three other carbon atoms. That is an unusual way for carbon to bond but it also makes a very strong bond.
Even though carbon nanotubes are so strong, they can be bent a lot without breaking (try doing that with a diamond!) Carbon nanotubes have a low density that is lower than aluminum. You might have noticed that a piece of aluminum feels pretty light. That is because it has a low density compared to other metals; a piece of aluminum is lighter than a piece of steel of the same size. Because of their low density, stuff made out of carbon nanotubes doesn’t weight much so they can be used to make strong ropes that are lighter than the strongest ropes we have today.
Some scientists are even working on a space elevator that will use a carbon nanotube rope to take us all the way up into space! Carbon nanotubes are already being used to make super light bicycles since bicycle racers need to carry as little weight as possible so that they can ride faster. You can heat up carbon nanotubes up to 1382°F (that’s as hot as lava from a volcano!) and they won’t melt or burn and they even conduct electricity and heat better than most other materials. All of these things make carbon nanotubes an extraordinary and one of a kind material.