A team of people who walk among visitors chatting, chanting and running was revealed on Monday as the latest artwork in Tate Modern's Turbine Hall.
The group, recruited by artist Tino Sehgal, will wander among thousands of visitors over the next three months.
It is the first time a performance work has been part of the Unilever Series at the gallery.
Berlin-based artist Sehgal's troupe work in four-hour shifts and strike up conversations with visitors, move around the place in formation and sometimes break into a trot before dispersing.
No photography or filming of the artwork, entitled These Associations, was allowed.
It is the 13th Turbine Hall commission and follows artworks such as a giant image of the sun, a series of giant slides and a vast crack in the floor. The exhibition opens to the public on Tuesday and continues until October 28.