This paper describes analysis of teaching instances that are part of an in-service preschool teachers programme about chemistry and physics in preschool. The aim is to develop knowledge about the communication established between teacher and children in relation to an object of learning, specifically the role of intersubjective communication in relation to an object of learning. A set of science activities with a specified object of learning was developed in groups of teachers and researchers. A qualitative analysis of the communication in relation to the chosen object of learning was performed. The focus of the analysis was excerpts representing differences in intersubjectivity related to the object of learning and what can be said to characterise the communication between teachers and children in these situations. The results show that intersubjectivity can occur in different ways with different consequences for children's opportunities to experience the intended object of learning. In connection to this, the importance of teachers having a mutual simultaneity in the communication with children about a specific content is highlighted. The teachers have to create links between the child's perspective and the object of learning. Intermediary objects of learning are discussed as supporting elements in the conquest of new knowledge.