With this study, we tried to find out the integration process of visualizations in the classroom and see the impact of a teacher training, to discuss and promote the use of visualizations in the Chemistry and Physics, on the conceptions of in service teachers in Brazil and in Portugal. One aimed to identify the preconceptions that these teachers presented early in the training, about the use of visualizations, and the possible changes that occurred after the involvement in the course. One tried also to characterize the pedagogical approaches that teachers used and the difficulties they encountered during the use of visualizations in the Chemistry and Physics teaching. In this study, we used a methodology that has its roots in qualitative research with interpretive guidance. In Brazil fourteen teachers of Chemistry and Natural Sciences of the Elementary and Secondary Education, distributed by fourteen schools belonging to the Greater São Paulo participated in this study. In Portugal had participated fourteen Physics and Chemistry teachers of Elementary and Secondary Education, distributed by eight public schools belong to the region of Lisbon. Since this study was applied in two contexts the strategy chosen was to two study cases, the case of Brazil and the case of Portugal. One used various instruments to collect data: naturalistic observation, questionnaires, interviews and written documents. In data analysis, we used the method of constant questioning and comparison to the saturation of the categories. The results revealed the existence of changes in conceptions about the use of visualizations. In Brazil's case the changes were more pronounced in the reasons for the use of visualizations and on the selection criteria of these resources. In this group, after training the teachers were more aware of the impact of visualizations in knowledge construction, in addition to the motivational role. Likewise, they proved to be more discriminating in the choice of these resources. In the case of Portugal, the changes focused on the selection criteria and the potential of these resources. In this case, the teachers showed tighter criteria for selection of these resources, and recognize other potentials, especially in terms of skills development. Regarding the approaches used in both cases prevailed the ones that deviated more from traditional teaching. Teachers tried to incorporate strategies into their teaching sequences based on constructivist views in order to involve students in their learning. Regarding the difficulties faced by teachers to integrate these resources into their practices, in the case of Brazil they stood either on the technical and pedagogical ones. The technical difficulties were related to the use of technology (simulations, animations) and the pedagogical difficulties were related to the uncertainty about the role of these resources in learning. In the case of Portugal, these difficulties were evident in the pedagogical level, including the role of the teacher in relation to these resources. This s...