I don't know, gum today—when I was a kid, you could stick it behind your ear and still guarantee it'd be there nine days later. Kids of today will never know the pain of having it scraped from their hair.
Thanks to a breakthrough by a British chemist, sticky streets could be a thing of the past. Professor Terence Cosgrove of Bristol University has come up with a chewing gum that dissolves in water and can be removed easily. And it's all to do with a new polymer, apparently.