How do I make a glass screen that becomes non-see-through when i pass electricity through it?

Question

I dont really have much details except that it may possibly work in a similar way to a calculator.

What i want todo is have the small glass screen (10 by 40cm) on one of my doors and be able to make it turn non see through by passing electricity through it, so that nothing can be seen trough the screen. Hope someone can help or knows where i can buy something like this.

Answer 1

I already answered this.

They are called "smart windows"

see

http://home.howstuffworks.com/smart-wind...