Taking place in the skies over London, the plazas of Rotterdam, and the hallways of museums worldwide, a new kind of art has emerged since the 1990s. Known as Relational Art, this controversial practice features audience participation in ways never before realised, often using new media and social networking. In this book, academic and artist Craig Smith outlines a rigorous theory of Relational Art, explaining why audience interaction and collective art production has become so relevant. He traces the movement from its beginnings with the Traffic exhibition and Nicolas Bourriaud's treatise Relational Aesthetics to the diverse and international scope of Relational Art today. Moving through a range of case studies, such as Olafur Eliasson's iconic Weather Project at Tate Modern, this book also reveals how Relational Art has affected the aesthetic, theoretical and economic forces shaping 21st century art. Craig Smith brings together ideas from artists, art critics, curators, philosophers and audience members to illuminate how Relational Art works are conceived, realised and experienced. Through a guided tour of thought-provoking and influential works, he demonstrates that Relational Art has permanently altered the nature of art and its global audiences.