The need to update and develop expertise is a never ending requirement of expert organizations (e.g. nuclear power organizations). Expertise development is a slow process. However, it can be supported in many ways. The SafeExpertNet (SAFEX) project applied interview and survey data to understand expertise and expertisedevelopment in Finnish nuclear power organizations. The results show that expertise development is extremely dependent on the individual employees themselves. Organizations can, however, provide many methods and opportunities that support expertise development. The SafeExpertNet project produced results that can be utilized in human resource management. The results and research findings provide support for organizations in their efforts to develop expertise of their employees. The actions of closest superior of experts and the functionality of the work group were strongly connected to the development of individual expertise. Moreover, collaboration crossing organizational boundaries offers good platform and prospects to develop expertise. Possible obstacles and facilitators of interorganizational collaboration were identified.