Dr Siún Nic Mhuirí is an Assistant Professor in Mathematics Education, in the School of STEM Education, Innovation and Global Studies, Institute of Education, DCU. She is interested in the agency and authority of teachers and students. Her research investigates the role of talk in classroom practice, and the design of initial and continuing teacher education. She is the lead on the Maths4All project, a large-scale engagement project which encourages dialogue between researchers and teachers, and between teachers themselves in professional learning communities. Siún is also an active member of the DCU research centre CASTeL, the Center for the Advancement of STEM teaching, and learning and until recently was co-leader of thematic working group TWG 19: Education, Mathematics Teaching and Teacher Practices, of the European Society for Research in Mathematics.