If you go look in your refrigerator or pantry right now, you will find that just about every package you see has a UPC bar code printed on it. In fact, nearly every item that you purchase from a grocery store, department store and mass merchandiser has a UPC bar code on it somewhere.

The bar code from a bottle of Selsun Blue dandruff shampoo

Have you ever wondered where these codes come from and what they mean? In this edition of HowStuffWorks, we will solve this mystery so that you can decode any UPC code you come across!