‘All the world's a net; or not?’ summarizes the extent and limitations of network science. There are warnings about the generalizations drawn from network theory, but the results of network science should not be underestimated, nor its future potential. The focus on topology is one of the strengths of the network approach, but it forgets many of the specific features of the elements. The graph approximation can then be inadequate, but models can be modified to include these features. Once data have been arranged as a graph, a careful interpretation of the results is essential. Most of the conclusions cannot be drawn by visual inspection; mathematical analysis is needed.