Students acquire numerous contents from arithmetic and geometry filed in their primary school education. Given that the proportion of geometric content in curricula is reduced, but they play an important role in developing logical reasoning and spatial awareness, the solution is found in creating a curriculum based on fundamental ideas. This paper emphasizes the fundamental idea of Operation with shapes. Its representation in the current Curriculum for mathematics for elementary schools and gymnasia is minimal, that is, it appears in the first and second grade of primary school in the form of a recommendation for using a tangram puzzle through which students would split shapes into parts and combine them back onto a plane. The tangram puzzle can help students understand geometric content, develop spatial awareness and geometric thinking. This paper provides an overview of the literature on the fundamental ideas and levels of geometric thinking, the overview of the literature on the tangram puzzle and its connection with mathematics, as well as the impact of using the tangram puzzle as a didactic tool on the development of students’ geometric thinking. In addition, the paper offers suggestions for activities with tangram puzzle for students in lower primary grades, emphasizing reading stories aloud and the impact of such an approach on students. As part of this work, a detailed analysis of the results of the research conducted in the 4th grade of primary school is presented to gain insight into the students' and teachers’ opinions about the experience of using a tangram puzzle in combination with reading the story Grandfather Tang's story. Through this study, an effort has been made to contribute to the discussion on more effective teaching of geometric content in classroom teaching and to highlight the need for implementation of the fundamental idea of Operations with shapes within the curriculum.