nanotubes to diamonds

I always knew that diamonds were carbon, graphite was carbon, etc. but I have never heard it put this way:

Diamonds are three-dimensional crystals of pure carbon. Two-dimensional carbon is graphite, while nanotubes are considered a one-dimensional form of pure carbon. (Technically, graphite and nanotubes have three dimensions, but the Z axis on graphite and the Z,Y axes on nanotubes are so small that they become irrelevant.)

- from a news.com article