The content of the expertise which young natural scientists try to gain by doing science in research groups is a relatively little-explored subject. What makes learning in such settings challenging is that a central part of the expertise is tacit. This study employs empirical methods together with a contextualized approach and interdisciplinary cooperation in order to reveal practicing nanomodellers' (N = 10) perspectives on their knowledge-building expertise, and on young scientists' expertise education. Modelling in the virtual world plays a major role in the science of these nanomodellers, as it increasingly does in many fields of science. This study therefore adds to our understanding of the nature of recent scientific knowledge building and expertise development, which can be used in the education of the scientists of the future.