Sh-h-h-h-h-h!! Top Secret... Crack the code of superspy science fun! Make your own spy sunglasses Write messages with invisible ink Hook up a secret alarm, and much more! Discover how spies use science to keep— or uncover— top secrets. Learn how to go under cover, master Morse code, and even build devices to see and hear through walls! These and dozens of other fun-filled activities give you an inside look at the science behind spy gadgets and tricks of the trade. All the activities are completely safe and can be done with everyday stuff from around the house.