What is darker than dark?

NASA engineers develop 'blacker than black' nanotubes.

Principal Investigator John Hagopian developed a new nanotech-based material that is 10 times more effective than black paint used by instrument developers to absorb stray light, which can contaminate scientific data. The sample on the left is black paint typically used to suppress errant light in instruments; the sample on the right is the new nanotube material.

This link will asplain all :

http://phys.org/news/2010-12-nasa-blacker-black-nanotubes-video.html