Everyone remembers having an Etch A Sketch and thinking you could draw beautiful pictures that would just end up looking like boxes. If you have ever wondered how the fun toy works, the guys over at What’s Inside on Youtube took a saw and a hammer to one and found exactly how they work.
The knobs control strings which pull a stylus in the respective direction based on the rotation of each knob. This stylus marks a glass sheet with Aluminum powder which makes the lines. Whenever you want to erase the picture and you shake the Etch A Sketch, the remaining powder covers the scratches and you can start drawing all over again!