This presentation contributes to the knowledge about how children learn about and explore mathematics in their everyday activities. Children´s mathematical encounters in play activities give them experiences as a base for education. The understanding of children’s mathematical encounters in play and teachers’ teaching is presented as teachable and learnable moments in ‘here-and-now’ situations. The data used for this study consists of video recordings of young children’s play in four Swedish preschools. In the presentation I use two examples to illustrate and discuss how children’s play can be a starting point for teachers’ teaching.  The results display that a teacher’s questions in play can support children’s explorations if the teacher observes, recognizes the mathematical content and asks questions.