Electrochromic materials change optical properties (darken/lighten) in the presence of a small electric potential difference, making them suitable for many applications. By fabricating porous films from crystalline WO3 nanoparticles (see figure), this state-of-the-art technology has been profoundly advanced. Significantly enhanced durability, increased charge insertion, and better kinetics have been demonstrated with an economical deposition process suitable for large-area applications.