This paper describes an investigation examining the constructing of a conceptual model of a selected natural phenomenon by children when using a pictorial computer simulation of that phenomenon. The paper concentrates on describing changes in children's conceptual models which appeared after an independent and spontaneous exploration process. The selected natural phenomenon was the variations of sunlight and heat of the sun as experienced on the earth related to the positions of the earth and the sun in space. Before the exploration of the natural phenomenon with the pictorial computer simulation children's conceptual models were at very different levels. S o m e children's conceptual models of the phenomenon were quite unidentified, and some others' very developed. Only some children's conceptual models contained misconceptions. The most significant change in children's conceptual models was that the interconnections of different things and phenomena began to be constructed and the construction seems to be in the direction of the currently accepted scientific knowledge. According to these findings it seems to be possible that an independent exploration by means of a pictorial computer simulation of a given natural phenomenon at a very early stage, w h e n children are spontaneously interested in those things, could help children in the formation of a correctly directed conceptual model of that phenomenon.