The purpose of the study is to find out what a group of seven-year-old South African children understand of their internal anatomy. The research is based on the premise that young children obtain most of their science knowledge through personal experience. Drawings are used to determine the level of young children's knowledge of systems and organs. The study also investigates whether there are significant differences between boys and girls' understanding as well as between children from a range of schooling contexts. Teachers were instructed to ask children to draw what they think is inside their bodies, using the language that is most familiar to the children (English, isiZulu, or isiXhosa). The findings show that children are able to draw individual organs, but are unable to show relationships between them. There were significant differences between different schools, but these differences were not due to different contexts. At Grade 1 level, boys were better able to represent what they thought was inside their bodies than girls. The findings show that the informal knowledge children hold of what is inside their bodies appears to be acquired by informal means, outside the school.