The aim of this study is to advance current understanding of the transactional processes that characterize students' sense-making practices when they are confronted with multiple representations of scientific phenomena. Data for the study are derived from a design experiment that involves a technology-rich, inquiry-based sequence of activities. We draw on "interaction analysis" to examine the work by means of which a group of upper secondary school students make sense of a number of different ways in which a physical phenomenon--a phase transition--is presented to them. Our analytical perspective, grounded in a cultural-historical framework, involves scrutinizing how the different materials emerge and evolve as signifiers for something other than themselves during teacher-student and student-student transactions. This approach allows us to trace the emergence of students' interpretations of the relations between phenomena and their diverse presentations without committing to any preconceived notion of what these presentations stand for. We describe how students' bodily and pragmatic actions become reified in conceptual terms and how these relate to lived-in experiences rather than to formal underlying concepts. Findings are discussed with regard to the central role of body and praxis in research on learning science with multiple representations.