To further this study, we have focused in the present work on the growth of the W18O49 nanowhiskers on the silica fibers using a new technique, i.e., the Reactor, which is an in-situ reactor in the scanning electron microscope (SEM) utilizing microelectromechanical systems (MEMS) heating chip (referred in the text as MEMS chip or MEMS heating chip) reaching also to in-situ transmission electron microscopy (TEM). This reactor was briefly described in a previous study. Here, the new Reactor and the growth process, i.e., the in-situ reduction of the -WO3/a-SiO2 fibers in the SEM and TEM, are described in great detail.