The aim of this paper is to illustrate how an empirical research interest in the transition between mathematics studies at secondary and tertiary levels generates a need for different theoretical approaches. From interviews with teacher students before and during their university studies in mathematics, three crucial aspects of the transition have been discerned; Mathematical learning objects, Mathematical resources and Students as active learners. Whereas the two former have both individual and social dimensions, the latter can be regarded as relational, constituting a link between the learning environment and the student in his or her intention to learn mathematics.