Go to settings and press "general." Then go to "Acsessibility." In the category Vision you will find a button that says "white on black" turn that on....
I will be showing you how to do stuff with your iPhone or iPod you didn't know or knew you could do. Most of these secrets work for iPads too. Camera stuff only works with iPod 4, iPhone 4 or 4S, and all iPhone- iPod 5s, Enjoy!
Step 1: Screen Shots
A lot of people know how to do screen shots, but for those who don't you press down the lock screen button down the same time you press the home button down, then quickly release. You will have token a picture of what was on your screen!