Early childhood education has gained increasing interest over the last decades, especially for its effect on the lifelong learning process. Particularly important for lifelong learning is the child’s self-confidence and positive emotions for learning experiences. Natural science is an important part of the preschool setting as it meets children’s natural curiosity of their surrounding environment while at the same time developing their social, linguistic and fine motor skills. However, very little is known about subject-specific concept development of preschool children, and most of the research efforts, so far, have focused on the fields of biology and physics. This project aimed to contribute to research method development as well as to increase our understanding of children’s emergent science and especially children’s emergent chemistry. The project takes as its basis cultural-historical theory and makes use of the methods derived from this theoretical perspective, i.e. play-based learning and the genetic research method. In order to analyse emergence, i.e. the process of concept development, a longitudinal study was performed, and a series of play-based learning activities with chemistry content were designed, implemented and assessed in an iterative manner. The study followed 20 three-year-old children over two years, and all the sessions were video-recorded using visualethnography. Results show the importance of the teacher’s role in planning activities, maintaining focus and moving the children beyond informal learning. The teacher’s own knowledge of natural science is key to building upon science content in the children’s discussions and moving the discussion forward while maintaining it within the children’s zone of proximal development. Data also show the importance of working with small groups of children due to the swiftness of the change in discussions and focus of children at this age. The abstract chemical concept chosen for this study was the concept of ‘small’. Initially the children did not have any experience of the sub-microscopic level, and it only began to emerge once the children had been provided with the visual experience of the transition from the macro to the microscopic level, which is a finding that may be one part of solving the decade long discussion on how to increase pupils’ and students’ understanding of the sub-microscopic level of particles.