The growth of W18O49 nanowhiskers from heated and partially oxidized tungsten filament in TEM was described by Hashimoto in 1960. The mechanism of the process was profoundly studied by Zhang et al. , who described mainly the mass transport during the oxidative W18O49 nanowhisker growth from tungsten filament. Here, the reaction was carried out in an environmental transmission electron microscope (ETEM). Alternatively, a direct reduction of tungsten oxide was observed in-situ in TEM , similarly in references. These results found that W18O49 nanowhiskers grow in an anisotropic fashion involving volatile tungsten oxides from oxidized metallic tungsten or by e-beam reduction of tungsten oxide.