In the Department of Physics, University of Helsinki, there are advanced physics courses designed for the needs of pre-service physics teachers. The starting point is that after introductory and intermediate physics courses, pre-service physics teachers know laws and definitions but the knowledge is quite fragmented and does not form coherent wholes. Graphical tools called didactical reconstructions were developed to help pre-service physics teachers to consolidate their physics knowledge. The idea behind the reconstructions is that "new" physics knowledge is always constructed based on previous knowledge (quantities, laws, theory). This means that every new concept is connected to previous concepts when it is formed; this is captured in the didactical reconstruction of processes. Then, when the knowledge is further constructed, the formed concept will be connected to other new concepts. This approach leads to the didactical reconstruction of structure: networks of quantities and laws, where the experiments and models construct the connections between quantities and laws. Here an overview and summary of the educational approach based on the didactical reconstruction is given for the first time. The results of the previously reported case studies show that the didactical reconstructions help students to connect the knowledge pieces into meaningful and more coherent wholes. These didactical reconstructions are now an integral part of our pre-service physics teacher education.