In an increasingly digital scientific landscape, the permanent and reliable identification of resources linked to research processes, its actors and their research products by means of Persistent Identifiers (PIDs) has become indispensable. However, the growing importance of PIDs in everyday research and increasingly in cultural contexts also increases the demands on their efficient usability. At the same time, users are confronted with a great variety of very different offers of PID systems and their possible fields of application. The project "PID Network Germany", funded by the German Research Foundation (DFG) and scheduled to run for 36 months, therefore aims to establish a network of existing and currently forming actors around the persistent identification of persons, organizations, publications, resources, and infrastructures in the field of digital communication in science and culture. This will not only optimize the dissemination and networking of PID systems in Germany, but also their embedding in international infrastructures such as knowledge graphs. The findings from the project will result in recommendations in a national PID roadmap for Germany, thus sharpening the vision of an interconnected and open scientific landscape. Under this guiding principle, the poster provides an overview of the different use cases of PIDs that we will focus on in the project's context. This is intended to illustrate the heterogeneous PID landscape with a focus on Germany and identify potential needs for action.