The present invention relates to a continuous, carbon fiber with nanoscale features comprising carbon and carbon nanotubes, wherein the nanotubes are substantially aligned along a longitudinal axis of the fiber. Also provided is a polyacrylonitrile (PAN) precursor including about 50% to about 99.9% by weight of a melt-spinnable PAN and about 0.01% to about 10% of carbon nanotubes. Other precursor materials such as polyphenylene sulfide, pitch and solution-spinnable PAN are also provided. The precursor can also include a fugitive polymer which is dissociable from the precursor polymer.