In this thesis, I present learning of preschool children and approaches to teaching the learning unit called The effect of solar radiation on temperature. In the first chapter of the theoretical part, I present the physical basis of solar energy and radiation as the source of energy exploited by human beings for their activities, while in the second chapter I present some of the most important learning concepts and teaching approaches for the preschool curriculum field of science. With the theoretical foundation, I formed the empirical part of the thesis and divided it into three parts according to the set goals. In the first part, I present the results of structured interviews that show preschool children's ideas about the Sun and solar energy. Then, with the help of the acquired information, I prepared a learning lesson in which I took into account different learning theories like constructivist teaching notions with cognitive conflict, learning presented as problem-solving and inquiry-based learning. Furthermore, I performed activities with preschool children aged five to six years. In the third part of the research I re-conducted the interviews and with that, I obtained information on how the learning process influenced the preschool children's perception on the Sun and solar energy. The comparison of the interview results before and after the lesson shows that there are some obvious changes in the preschool children's ideas about the Sun and solar energy that can be attributed to proper learning and teaching approaches.