Children of early and preschool age encounter the basics of geometric concepts in their environment every day. Given that the development of geometric thinking is not affected by chronological age, the goal of this thesis is to examine at which level of geometric thinking according to van Hiele's theory children of early and preschool age are at. At the beginning of the paper, the development of van Hiele's theory on the development of thinking is described. Then the levels of geometric thinking are listed, namely: the level of recognition, the level of analysis, the levels of informal deduction, the level of formal deduction and the level of rigor. In addition, objects and products of geometric thinking are listed for each level. Each level of learning is then described and their characteristics are presented. The basic characteristics of van Hiele's model of thinking development are also described, as well as the stages of learning that can be useful in planning and organizing classes, as well as preschool activities. For the purposes of this thesis, a research was conducted in which children of early and preschool age participated. They were offered two tests to determine how they perceive geometric shapes in their everyday life. At the end of the paper, examples are given for encouraging the development of geometric thinking in children of early and preschool age.