Aerosmith's Steven Tyler and Joe Perry performed this "Dream On" tribute to those who lost their lives, those who were injured and all who were touched by the Boston Marathon bombing last year.  ESPN's E:60 also interviewed Tyler and Perry about the performance.

Today, for the 118th time, the storied race is taking place, with the second largest number of competitors ever.  And the crowd is expected to be about a million - double the usual size.