In a transmission electron microscope, CuCl particles were irradiated by a convergent electron beam (CEB, 200 kV, 200 pA/cm2, beam diameter of ca. 1-2 μm) to induce growth of copper nanostructures. Upon CEB irradiation, Cu nanoparticles (5-20 nm in diameter) were formed from commercial CuCl. Using synthesized CuCl encapsulated in permethylpolysilane, growth of polycrystalline copper nanowires (50-200 nm in diameter and up to 30 μm in length) was observed. Evolution of Cu nanoparticles from the synthesized CuCl was observed from the positions with apparent incomplete encapsulation. The effect of polymer encapsulation, acting as a soft template, is shown to be important to influence the nanostructure growth. The observation supports the vapor-solid reaction growth model.