Materials science has a dark side. Researchers report that they have made the world's darkest material from a low-density, vertically aligned array of carbon nanotubes (Nano Lett., DOI: 10.1021/nl072369t). The material's total reflectance of 0.045% is three times lower than that of a phosphorus-nickel alloy that was previously identified as the world's darkest substance, and it's more than 30 times darker than the standard black benchmark used by the National Institute of Standards & Technology. A team led by Shawn-Yu Lin of Rensselaer Polytechnic Institute and Pulickel M. Ajayan of Rice University prepared the near-perfect black material. Carbon nanotubes are known to be good at adsorbing light, but the material's engineering also enhances the nanotubes' inherent blackness. The researchers hypothesize that when arranged in a low-density array, the deep pores between the tubes act as a light trap. Nanoscale surface roughness also keeps reflection to a minimum. If the material behaves similarly toward ultraviolet and infrared radiation, it could be used as a stealth coating for defense and other applications.