Created by a 3M scientist, Scotchgard is a substance that helps prevent dirt from staining fabric.  At first, the scientist was trying to make a synthetic rubber to be used in airplane fuel lines. By accident, some of the new substance spilled on her assistant’s canvas shoe, and they couldn’t get it off. As the tennis shoe grew older, it got dingy–everywhere except where the substance had spilled. Three years later, after some trial and error, they had invented Scotchgard.