The aim of mathematics education research is to develop comprehensive understandings of the problems of mathematics teaching and learning, and the ambition is, at least in the long run, to support the development of institutionalised teaching-learning practices. Looking back at the attempts to structure syllabi and other curricular materials and to study student learning in clinical settings in the past, it is disappointing to see the dismal results of the efforts. There is "a complexity" involved in mathematics education that goes beyond the subject itself and beyond individual students' cognition. The papers in the present issue of the Journal of Mathematics Teacher Education (JMTE) in different ways and to different extents reflect this move beyond an interest in mathematics per se and in individual students' learning. It is increasingly acknowledged that the student population in many countries in the West is becoming increasingly diverse, and that mathematics plays a significant societal and political role in and beyond educational contexts. We sometimes tend to write about teachers' knowledge and beliefs, about noticing, and even about equity as if contextual issues do not matter much. But they do matter, also within the countries that dominate our international journals at present. The "full complexity" of mathematics teaching and learning is to a great extent contextual complexity.