Book excerpt: QUICK: Name the most powerful and complex supercomputer ever built. Give up? Here's a hint: It's housed in your head and it's the one thing that makes you YOU. Your brain is mission control for the rest of your body and steers you through life. Not bad for something the size of a softball that looks like a wrinkled grey sponge In this fascinating, interactive book -- a companion to the National Geographic Channel hit show - kids explore the parts of the brain and how it all works, brainy news nuggets from a neuroscientist, plus fun facts and crazy challenges.