Is there anything carbon nanotubes can't do? Scientists recently described a way to make large quantities of florescent carbon nanotubes. The image at left shows a vial of nanotubes exposed to an ultracentrifuge, with the florescent nanotubes forming the purple layer. The florescence of nanotubes is determined by their supramolecular arrangement - as we see in the image, when a nanotube clump is too big, it looks black when suspended in a solution, and when it's too small, it looks clear. The florescent band is right in the middle. Nanotube florescence is especially remarkable because it lasts for months, unlike Quantum dots, which last a few days, or florescent proteins, which only survive a few hours.