We love this made-for-kids series of videos, Circuit Playgroundby MIT engineer and Adafruit Founder Limor Fried (in the pink hair) and her robot friend ADABOT. For this excellent DIY project — and to find out what’s going on inside of the batteries that you use — get some lemons, pennies, galvanized nails, some aligator clips, and an LED, then watch their second video in the series, B is for Battery.

And if you missed it, watch A is for Ampere.

See more videos about...