In contrast to a vast literature that provides information and guides about focus groups as a methodological tool, this book is an introduction to understanding focus groups as analytical means exploring socially shared knowledge, e.g. social representations of AIDS, biotechnology or democracy, beliefs and lay explanations of social phenomena. The main emphasis of the book is to examine how to analyse interaction and ideas expressed in focus groups. The book considers, first, different kinds of dynamic interdependencies among participants who hold the diverse and heterogeneous positions. Second, it explores circulations of ideas and contents in focus groups.