Paying it forward is a concept that's simple in execution, but can have wide-ranging, and sometimes life-changing, effects.
One man whose life changed on September 11, 2001 pledged to pay forward the kindness he was shown on the day of the attacks, and has been continuing his mission ever since. Kevin Tuerff says he was blown away by the kindness of strangers, and has made it his life's work to pay it forward.