A group of students at PS 161 in Harlem got the surprise of their lives Tuesday when music superstar Beyonce showed up to participate in their flash workout.

The event was all tied to Michelle Obama's Let's Move! campaign, designed to fight childhood obesity. Beyonce, of course, is a big component of the campaign; she filmed a now-viral song and music video for it called 'Move Your Body,' which the students recreated in the video.

Check it out below, if only to see how well they kept their cool - not to mention moves - once Beyonce showed up.