This paper documents a case of model-building in biology through microanalysis of one student's interaction with 'Science for Living: The Circulatory System' (SFL), an interactive multimedia resource prototype for research. When SFL was used in a technology-rich, tenth grade (15-16 years of age) biology classroom, extensive data ranging from preconceptions tests to videotapes, projects and computer logs of work sessions were collected. This paper describes the student's learning goals, gains and activities with particular attention to interactions with representations, then contrasts them with those of classmates. The representations accessed by the learner were analysed with respect to contributions to mental models, the challenges posed by the representations and the effectiveness of the interface in overcoming those challenges. This rich and systematic description of model-building with multimedia enabled the formation of an initial model of model-based learning in this context.