We report a Novel type of WO3 nanostructure, i.e. nanorolls obtained as self-assembled thin film on a transparent conductive substrate. The mild conditions of preparation, avoiding the use of HCl, result in a eco-friendly hydrothermal method with reduced crystallization time. FESEM and HR-TEM show that WO3 nanocrystals are made of rolled nanoflakes with a telescope-like appearance in their tip. For their nano-porosity, electrochemical accessibility, good adhesion to substrate and the envisaged presence of nanocavities between WO3 layers, these material hold tremendous promise for nano-electronics, electrochromic devices, water photo-splitting cells, Li-ion batteries and nano-templated filters for UV radiation.