Carbon fibers are manufactured from polyacrylonitrile (PAN) or pitch precursors. PAN fibers are produced by wet spinning a PAN solution, stretching, and heating the fibers to form ladder structures. The fibers are then carbonized and graphitized by heating in an inert atmosphere. This process orients the carbon atoms into aromatic rings in parallel planes, resulting in high tensile modulus. Pitch fibers are made by melt spinning mesophase pitch into fibers, stabilizing, and then carbonizing and graphitizing through heating, which similarly orients the carbon atoms. Both precursors can produce high strength carbon fibers with varying moduli depending on the heat treatment temperature and use of stretching.