As Simon (1981) has pointed out, coming to characterize phenomena as functional systems is fundamental for our understanding of the natural and man-made worlds. Yet little is known about people's propensities for making such characterizations. In contrast to previous research that has focused on unfamiliar, opaque systems, the study reported here investigated experts and novices relative use of structure-function relationships to understand a familiar, inspectable system--a bicycle. As the study shows, the experts, but not the novices, spontaneously and consistently utilized a systems approach to characterize this familiar object.