By carefully controlling the experimental parameters, large-scale nanosponges of group II-B metal (Zn and Cd) on Si substrates are fabricated through a vacuum vapor deposition route (VVD). The as-prepared products are systematically characterized by the techniques of powder x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is shown that nanosponges are composed of network nanowires, which are 20-250 nm in diameter and hundreds of micrometers in length. On the basis of the time-dependent experimental findings, the nucleation and growth of the nanowires have been elucidated. Moreover, the melting behavior of a single ultrathin zinc nanowire was observed in situ under the irradiation of an electron beam during the TEM measurement for the first time, showing that the melting point of the ultrathin zinc nanowire is significantly lower than that of the bulk.