The notion of exploratory modeling constitutes a powerful heuristic tool for historical-epistemological analysis and especially for studying concept formation. I will show this by means of a case study from the history of particle physics: The formation of the concept of “strangeness” in the early 1950s at the interface of theory and experiment. Strangeness emerged from a broad space of possibilities opened up by exploratory modeling by authors working in communication and competition, and constructing both new questions and new answers. A systematic focus on exploratory modeling also helps compensate a bias towards the “right” developments still often present in historical investigations of theoretical work.