The value of children's drawing and writing in science lies in its potential to assist children in making observations, remembering events, and communicating understandings. However, a neglected aspect of children's representations is that they can serve the teacher as guide to children's understandings and as a diagnostic tool. By creating their own journal pages, children are able to depict their ways of seeing and understanding the science phenomenon, constructing or reconstructing the phenomena through their own lens of experience. The objective of this study was to investigate how children represent science phenomena and activities on the journal page. The sample size consisted of 16 first and second grade students participating in a one-week intercession class on earth materials. Data sources included the children's self-produced science journals and field notes based on children's talk and activity. This qualitative and naturalistic research showed that the majority of the students used their science journal pages to represent either the science materials or the physical activity itself. Their understanding was characterized by a simple recording of what happened in the activity. Only a few children represented an understanding of the science processes of mixing and separating as dependent on the size differences between the earth materials. (Contains 5 data tables and 3 figures.) (CCM)