Hélio Oiticica (1937–1980) altered the Brazilian art scene, and his works broke with accepted conventions. His oeuvre was of great importance to the breakthrough of Tropicália, the cultural movement that protested the repressions of the military regime. Experiment, proposition, participation and environment are the key words that place Oiticica’s art firmly in the 1960s and 1970s. Coming from painting, he developed into one of the protagonists of a new concept of art: he actively involved the viewer in the presentations of his multimedia works, while the works–colorful, accessible, tangible, or wearable like a piece of clothing–filled the space. This participatory kind of eventful art is related to the democratization of the concept of art, as conceived by Joseph Beuys. Oiticica’s writings and records, collected in this in publication, comprise a fascinating document of the transition from modern to contemporary art.