The aim of this special issue is to analyze the dynamics of differentiation in education. In particular, the conceptual term of differentiation will be explored by focussing on various arenas of curriculum making. ‘Differentiation’ entails much more than instructional or didactical considerations and strategies: At the heart of the curriculum making lie ideas and assumptions about socio-cultural and political processes and their consequences. Curriculum developments and differentiation processes connected to it are highly dynamic in nature. They emerge across various spatial and temporal contexts within diverse discursive settings. This special issue aims to elaborate on broader, sociologically and historically oriented concepts of differentiation in education systems. This brief introduction to the special issue is disposed of in the following way. Firstly, we define the term differentiation. We do this with a sociological meaning and then connect it to education research. In particular, concerning the latter, we define research gaps, which this special issue aims to approach. Then, we present the six contributions to this edition with their individual contribution to understanding differentiation in education. Finally, we discuss the contributions’ similarities and differences.