In this talk, we focus on the analysis of bibliometric networks, and in particular on the detection of communities in these networks. We start by demonstrating VOSviewer, a popular software tool for visualizing bibliometric networks. We discuss the techniques used by VOSviewer for visualizing bibliometric networks and for detecting communities in these networks. We pay special attention to the close relationship between visualization and community detection, and we discuss the unified approach to visualization and community detection that is implemented in VOSviewer. We then shift our attention to community detection in very large citation networks, including millions of publications and hundreds of millions of citation relations. We show how community detection techniques can be used to construct highly detailed classification systems of science. We also discuss applications of such classification systems to science policy questions. Finally, we demonstrate CitNetExplorer, a new software tool in which community detection techniques are used to support the large-scale analysis of citation networks. We use CitNetExplorer to analyze the citation network of publications on network science and in particular on community detection.