Nanoscale carbon materials including carbon nanotubes and nanoparticles have interesting and, in many cases, unique properties. Specifically, we have been developing methodologies to separate metallic and semiconducting single-walled carbon nanotubes (SWNTs). The significant progress in the effort will be highlighted, and the targeted applications of the separated materials will be discussed. More recently, we have found that quantum-sized carbon particles can be made highly photoactive upon simple surface passivation, exhibiting strong photoluminescence in both solution and solid-state (thus dubbed as “Carbon Dots” or “C-Dots”). The C-Dots may find applications alternative to or beyond those of traditional semiconductor quantum dots. For example, they may be derivatized to recognize and bind to biologically active species. Some representative experimental results will be presented, along with discussion on mechanistic issues.