Electromagnetic irradiation of functionalized fullerenes in an oxygen-free environment induces conversion of the functionalized fullerenes to carbon nanotubes, carbon nanohorns, carbon onions, diamonds and/or carbon schwarzites. The carbon nanotubes can be multi-wall carbon nanotubes. Advantageously, the subject invention can be used for in-situ synthesis of carbon nanostructures within a matrix to form a carbon nanostructure composite, where positioning of the carbon nanostructures is controlled by the manner of dispersion of the functionalized fullerenes in the matrix. Carbon nanotube comprising features, such as electrical connects, can be formed on a surface by irradiating a portion of a functionalized fullerene coating with a laser beam.