The paper introduces a new information-theoretic approach to reveal community structure in weighted and directed networks. The method decomposes a network into modules by optimizing the compression of information flows on the network, resulting in a map that simplifies and highlights the regularities and relationships within the network. The authors illustrate this method by creating a map of scientific communication based on citation patterns among over 6000 journals, revealing a multicentric organization with fields varying in size and integration into the scientific network. The map shows a bidirectional flow of information along the backbone of the network (physics, chemistry, molecular biology, and medicine) and a directional pattern of citations from applied fields to basic sciences. The approach is compared with modularity optimization, demonstrating its effectiveness in capturing the interdependence of flows in networks. The paper also provides a detailed description of the map equation and the computational procedure used to minimize it, along with the maps of science and social sciences.The paper introduces a new information-theoretic approach to reveal community structure in weighted and directed networks. The method decomposes a network into modules by optimizing the compression of information flows on the network, resulting in a map that simplifies and highlights the regularities and relationships within the network. The authors illustrate this method by creating a map of scientific communication based on citation patterns among over 6000 journals, revealing a multicentric organization with fields varying in size and integration into the scientific network. The map shows a bidirectional flow of information along the backbone of the network (physics, chemistry, molecular biology, and medicine) and a directional pattern of citations from applied fields to basic sciences. The approach is compared with modularity optimization, demonstrating its effectiveness in capturing the interdependence of flows in networks. The paper also provides a detailed description of the map equation and the computational procedure used to minimize it, along with the maps of science and social sciences.