The participatory turn in science communication embraces a range of activities and concepts, from citizen science to multistakeholder dialogue and public access to information and even juridical redress, when necessary. Public participation in science breaks with the underlying assumptions of public understanding of science and scientific literacy approaches: that scientific knowledge in some sense is privileged, that understanding the science will lead to appreciative attitudes toward science and technology in general, and that controversial issues involving science and the public are rooted in public misconceptions of science. This paper uses the dialogic space proposed by Callon et al. to explore relationships between public and science. The dialogic space spans collective versus scientific dimensions. The collective (or public) is constituted by aggregation (opinion polls) or by composition (organized groups of concerned citizens), whereas scientific research is characterized as either secluded research that is performed exclusively by expert scientists or as collaborative research that involves lay people in the production and communication of knowledge.