A polyhedral oligomeric silsesquioxane (POSS) macromonomer with the cage structure of $Si_8O_{12}$ consists of an inorganic silicon and oxygen core surrounded by organic groups on the corners. In this study, POSS was blended with polyurethane and electrospun to produce organic/inorganic hybrid nanofibrous mats. Silica was formed on the nanofibers after exposing the nanofibrous mats to silicic acid under ambient conditions. Structural characterization was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The morphological difference resulted from the condition of water evaporation and the hybrid with and without the POSS after silicification. The thermal behavior was examined by thermogravimetric analysis (TGA). These 3D inorganic-organic hybrids have potential applications as templates for photonic materials, novel membranes, and scaffolds for hard tissue.