Piero Manzoni was a pioneer of Conceptual Art and a member of the Gruppo Nucleare, which antagonised any sort of academicism. Like his fellow artists Alberto Burri and Lucio Fontana, Manzoni experimented with new materials such as plaster and enamel, and that is how he created his first 'Achromes'. These colourless, plaster-primed and structured canvasses permeated Manzoni's complete oeuvre. Manzoni's relief pictures greatly influenced the members of the ZERO group, with whom he exhibited his works. This in turn led to the creation of Manzoni's first pneumatic sculptures, and he started signing living bodies which he then declared 'works of art' with a certificate.