Complex sentence: On May 26,2010, Willow Garage held a graduation party in which the 11 PR2s were introduced PR2s "danced" with humans while being led by their grippers.
Split into simpler sentences: On May 26,2010, Willow Garage held a graduation party in which the 11 PR2s were introduced. Some PR2s "danced" with humans while being led by their grippers.