Step 1: Materials and Components
Paper, we've used thick cartridge paper, but copy paper would work fine
3V Button Cell Battery
White LEDs or whatever colour you want.
3V Button Cell Batteries UK: Farnell / US: RadioShack
LED's UK: Farnell / US: RadioShack
* Make sure you buy several Batteries and LEDs for all your projects in advance to save on shipping charges, and so you don't have to wait to do fun tutorials.