In this book I report from a study of the development of algebraic thinking of three teachers, from lower secondary school, and a didactician from a university in Norway (myself). The book offers an account of the relationship between the participants'' development of algebraic thinking and the processes related to the creation and development of a community of inquiry. In addition, it presents elements of the relationship between the teachers'' development of algebraic thinking and their thinking in relation to their teaching practice. The results of this study indicate that the participants’ development of algebraic thinking is deeply interwoven with the processes related to the creation and development of the community of inquiry. Overall, the book contributes to a better understanding of issues related to collaboration between in-service teachers and a didactician from a university, while focusing on the development of algebraic thinking. Implications are also suggested concerning the way algebra could be addressed in schools.