The present invention is directed to eyectrochromic, supercapacitor yarns and the related fabrics. An electrochromic yarn formed by two interwind threads has been invented. The yarn is electrically isolated by a transparent, uncolored polymer. Each thread is the superposition of three concentric layers. The most internal one, the core, has the function of support and/or conductive layer, the second one is the eiectrochromic layer containing conductive nanoparticies, the third layer is a polymer dielectric blend. The yarns described above allows to generate electrochromic fabrics in which the colour can be varied by the application of small electric voltages fed by a battery with variable power supply controlled by a microprocessor connected to a smartphone via Bluetooth technology. A specific application on the smartphone allows to change the voltage supply to the fabrics, in order to get the desired chromatic change.