Throughout my university career I have been exploring mathematics classrooms at lower secondary level, in particular with respect to teacher pedagogy and curriculum materials, and internationally. Comparing classroom in England, France and Germany has helped me to identify 'underpinnings', cultural and educational traditions that shape pedagogic practice. Furthermore, I have been working with teachers on curriculum materials, including textbooks, to develop their mathematical knowledge in and for teaching. More recently, I have extended my research to include investigating student identity, the constitution of the self as a student and as a learner of mathematics, in particular when transiting from upper secondary school/college to university mathematics. For this I have mostly used socio cultural perspectives and considered transition from the perspective of social practice and activity theory.