In this paper we present a way to study science learning on a discursive level in a teaching activity designed for a museum of natural history. We used here an analysis of practical epistemologies. The method, which allows a description of students' meaning making in socially shared practices, has been used previously to analyze learning in various school practices. The data presented in this study proceeded from a videotaped activity of the educational program for student teachers at the Swedish Museum of Natural History in Stockholm. The activity utilizes a variety of dioramas with preserved animals in scenes that reproduce their natural environments and behaviors. In small groups, and without the help of exhibition text, student teachers discuss, interpret, and explain the different scenes displayed in the dioramas. Through the analytical framework used in this study, we are able to study people's meaning making through the development of their discourse in encounters with the diorama and with their previous experiences. We suggest that this approach offers a practical and useful way to describe and analyze people's actions in informal learning settings. (Contains 2 figures and 17 notes.)