The first report on the production of Carbon-Dots, quite tellingly, featured an almost “accidental” discovery of fluorescent carbon nanoparticles through an unrelated synthetic pathway—a byproduct in arc-discharged soot generated for the synthesis of carbon nanotubes (Hola et al., Nano Today 9:590–603, 2014 ). Intriguingly for the researchers who carried out the experiments, some of the “impurities” identified in the crude nanotube soot were fluorescent (Fig. 2.1), and furthermore different fractions yielded different fluorescence wavelengths (e.g., different colors). Fig. 2.1“Fluorescent carbon” nanoparticles identified in agarose gel. The fluorescent fragments were identified in suspensions of single-wall nanotubes (SWNTs). Shown is an agarose gel image under 365 nm illumination. a Crude SWNT; a fluorescent band is apparent; b purified fluorescent carbon; c–e carbon nanotubes; f fragmented SWNTs. Reprinted with permission from Xu et al. . Copyright (2004) American Chemical Society.