Electrochromic materials are substances that change color or opacity when an electric voltage is applied. These materials can be used in various applications, such as smart windows, which can adjust their tint to control light and heat entering a building, improving energy efficiency. The technology behind electrochromic materials involves the movement of ions within the material, leading to a reversible change in color. Common examples include tungsten oxide and polymer-based films, which are often used in displays and automotive applications to enhance privacy and reduce glare.