Play is considered an important aspect of Early Childhood Education and Care. However, the relationship between play and learning is often taken for granted both in research and praxis. In this article, we study our own research group's empirical work over a 40-year period, and how we have used the concepts of play and learning. We observed that how the relation between play and learning has been conceptualised, have gone through changes during this period in a number of ways, in line with other research, influenced by policy, and theorised grounded in empirical studies towards what is called Developmental Pedagogy. Children's perspectives and teacher's sensitivity and responsiveness have been important features of the process of developing the preschool pedagogy in which play and learning are central. The relationship between play and learning are conceptualised differently, at the same time as the content (sometimes called curriculum in the English-speaking world) are equally important in the early as well as latest steps of this development in research.