This study explores how experimenting with Complex Instruction can broaden teachers' perspectives and develop understanding of the classroom as a complex social and cultural system. It critically presents and interweaves data collected during ethnographic research, which was carried out with a group of in-service teachers, plus four workshops which involved pre-service teachers. Complex Instruction often provides teachers with an unusual experience, which may cause "dis-orientation." It is precisely this uncertainty that moves teachers to investigate their own beliefs and dispositions towards teaching and learning, as well as imagining new scenarios for their classes and for themselves as educators. This state of uncertainty strengthens the ability to raise questions about their own practice and makes them more aware of the responsibility of their role in developing a more equal participation in class. The article argues how Complex Instruction can promote a process of "reflexivity-in-action" and therefore challenge teachers' professional identity.