Circumstances in school change and teachers constantly face different obstacles. One of these includes dealing with heterogeneity and diversity in chemistry classes. Future chemistry teachers need to be aware of the differences in their classrooms. They must be prepared to diagnose and handle differences in order to obtain the best possible learning outcomes for their students. The present paper presents a cooperative project, which develops and evaluates teacher training modules at the University of Bremen (Germany) and the University of Helsinki (Finland). The seminars are based on a 3-step model which will be described as well. This model focuses on the initial sensitization of student teachers for heterogeneous chemistry classes (first step) and qualifying future teachers to diagnose (second step) and deal with heterogeneity and diversity in chemistry classroom (third step). Examples taken from the courses at both universities will be presented and preliminary evaluation results are given and discussed. First successes of the three steps of qualifying student teachers are recognizable in both countries. The courses in both countries show a short section from the teachers training program for the Bachelor and Master degree. All students attend different school in an internship after or during the courses.