The authors introduce the exploration of object-oriented basic concepts as a new approach to object-oriented modelling (OOM). While other subjects have a long tradition in learning by discovery with suitable learning aids (e.g. experimenting installations of the scientific subjects), Informatics at first has to define and to develop such learning aids. Therefore software development environments have been analysed and understanding promoting as well as understanding hindering functions have been identified. In detail the understanding promoting functions "support of the syntactic correctness of a model", "promotion of the logical correctness of a model" and "visualization of abstract concepts with change of the observation perspective" and the understanding hindering function "error avoidance by ban of action" as well as the fact, that the fundamental ideas of OOM are presupposed, were found. By these findings, design criteria of the Didactics of Informatics for so-called exploration modules, learning aids for the exploration of object-oriented basic concepts, are derived. These are the criteria "basic concepts on different abstraction levels" and "synchronization, transformation and evaluation of diagrams". Finally the role of exploration modules as a lesson medium is discussed and the application of the exploration by learners is worked out. Especially the change between different views of an object-oriented model to ensure completeness and consistency is stressed.