The Rolling Stones 50 and counting tour rolls on. The latest special  guest was none other than Taylor Swift who joined the Stones on stage in Chicago.Taylor joined Mick Jagger on the Stones hit "As Tears Go By"

Taylor Tweeted:  "Filing this under 'never in my wildest dreams'. Thank you @RollingStones for inviting me to Chicago to sing with you."

Check out the video below...