This study is part of a project regarding explanatory illustrations in science education. Research questions here concern how pupils use and make meaning from illustrations in a science textbook. Electricity was chosen as the subject. Video data was collected in 8 sessions, each with a pair of pupils, 10-11 years of age in one school in Sweden. Communication within the pairs and with the interviewer was analyzed. The children also drew a picture of a battery and explained its function using this drawing. The most striking result was an almost complete lack of transparency for the scientific information in the illustrations. Regardless of previous knowledge, pupils were almost never able to collect new information on their own or together with their peer. As long as the visual information matched previous knowledge they could explain the content, but as the complexity increased, they were lost. They then either expressed their incomprehension or carried on to argue for evident misconceptions, not realizing that the illustrations were contradicting them. Together with the interviewer, pupils could eventually identify central scientific messages and where their previous understanding was challenged. One conclusion is that scientific illustrations can drive scientific in-depth discussion. However, the main conclusion is that pupils are not trained to interpret multimodal information themselves and that teachers and textbook authors therefore risk overestimating pupils de-coding abilities.