They tell you how to make: a USB flashdrive within a battery ( the battery does work ), a listening device within a book, a communicator that sends sound over a laser ( by itself it isn't great, but think of the possibilities . . . . ), a chess set that when the pieces are moved correctly, a box unlocks, an alarm that goes off with your recording when an object is moved, that cellphone thing, a survival kit, hollow-bolts, self-melting objects ( like keys that melt on your command ), and invisible-ink printers. That is a mouthful, so subscribe to the digital edition ( like me ) and get it all in a nicer format. I did not intend that to be an advertisement, but it came out that way.