This paper reports on a combined research-development project conducted in collaboration between researchers and preschool teachers in three Swedish preschools. The aim is to investigate how ongoing preschool activities may become the starting point for mathematics teaching in which toddlers are given the opportunity to distinguish necessary aspects of numbers. One challenge in preschool education is the balance between children’s previous experiences and interests versus offering them new experiences and challenges towards a learning goal. In the article, empirical examples are used to illustrate how small changes in an activity may open up opportunities for toddlers to discern different critical aspects of numbers without losing the activity’s initial intention. Principles for how early numeracy education can be designed to achieve this balancing act are presented and elaborated on.