This doctoral project focuses on the use of picture books to stimulate the mathematical development of young children (3-6 year olds). Particular attention will be paid to the interaction between the teacher and the child during the reading aloud of picture books. The doctoral project will consist of a series of empirical studies in ecologically valid settings. Each of these studies will focus on the interaction between the (future) teacher and the child during the reading aloud of picture books. Based on observational research, the spontaneous teacher-child interaction and the alignment of this interaction with the child's mathematical competencies can be mapped. Through intervention studies, targeted training and professionalization of (future) teachers can be used to optimize this interaction in order to maximize learning gains for all children.