Nanofibrous materials, which are some of the one–dimensional nanomaterials, have unique properties compared to their bulk solids (e.g., high specific surface area, high electrical conductivity, and good electrochemical activity). They are easy to form a 2–D or 3–D network structure. This network structure enables an efficient charge transport through the network backbone and an efficient chemical reaction at the surface. This reports describes thin–film applications of nanofiber networks in energy storage and optoelectronic devices.