Carbon nanotubes--those minute cylinders of carbon poised to revolutionize the fields of materials science and electronics--just got even smaller. According to two reports published in the November 2 issue of the journal Nature, scientists have discovered the smallest stable carbon nanotubes known. Teams led by Lu-Chang Qin of the NEC Corporation in Tsukuba, Japan, and Z. K. Tang of the Hong Kong University of Science and Technology observed these tiny tubes, which, at 0.4 nanometer in width, represent the theoretical limit in smallness. Smaller than strands of DNA, carbon nanotubes were first described in the early 1990s. Since then they have captured the attention of scientists around the world who envision using them to build better televisions, batteries, wireless communications systems and to strengthen materials, among other things. In addition to great strength for their low weight, these tiny variations on ordinary graphite also offer good heat conductance and intriguing electronic properties. Still, researchers are just beginning to understand and exploit nanotubes, so exactly how useful they might be remains to be seen.