The easiest way to visualize how nanotubes are built up is to start with graphite, the most stable form of crystalline carbon.
Graphite consists of layers of carbon atoms.
The weak interlayer coupling gives graphite the property of a seemingly very soft material, the property which allows to use graphite in a pen to write with. This mapping condition ensures that, again, only hexagons can be found on the surface of the cylinder. For any other values of n and m the tubes are called chiral tubes since in those cases the chains of atoms spiral around the tube axis instead of closing around the circumference. Moving the mouse into the lower right field with the nanotube image the tube can be rotated by dragging with the right mouse button pressed. In our idealized construction the tubes are infinitely extended along the axis of the tube.