Nanocrystalline diamond thin films have been prepared using hot filament CVD technique with a mixture of CH4/H-2/Ar as the reactant gas. We demonstrated that the ratio of H-2 to Ar in the reactant gas plays an important role in control of the grain size of diamonds and the growth of the nanocrystalline diamonds. In addition, we have investigated the growth of carbon nanotubes from catalytic CVD using a hydrocarbon as the reactant gas. Furthermore, focused ion beam technique has been developed to control the growth of carbon nanotubes individually.