Windows are a vital visual opening to the outside world for both the driver and passengers. The first windows were just a flat panel of glass, but modern windows are made out of layers of materials such as plastic and more advanced polycarbonates. Some rear windows have defrosting elements built into them, which are just thin metal strips which can quickly heat up the window.
Some windows on the sides of the vehicle can open up by receding into the door or body of the vehicle. Initially, the only means of doing this was a crank, but many modern cars have button-operated windows. These work by moving a cable loop which is connected at one point to the mount the window is attached to. The electric motor is normally off, and the direction it turns depends on the polarity of the electricity flow, which is chosen by the button.