An introduction to the emerging science of networks, with applications to biology, social science, engineering, and other fields. Students will learn about the field's origins in graph theory, and the surprising properties of real-world networks such as the small-world effect. They will also learn to analyze the rich structure present in networks through degree correlations, communities, and motifs. Finally, it will discuss how networks shape the spread of large-scale failures like power blackouts and epidemics.