Electrochromic devices (ECDs), which can dynamically vary optical properties under applied specific voltage, have been actively studied for use in applications requiring human comfort and energy efficiency (i. e. smart windows and electronic displays). In order to improve the electrochromic (EC) performances, many researchers have been using nanomaterials. In this respect, in the present study, we highlight some of valuable examples using WO3 from unique nanostructures to quantum dots (QDs) and discuss the core relationship between nanostructuring and EC performances. In particular, the present study proposes major impact on the novel approach using QDs to upgrade technical value and application of ECDs.