There are networks in almost every part of our lives. Some of them are familiar and obvious: the Internet, the power grid, the road network. Others are less obvious but just as important. The patterns of friendships or acquaintances between people form a social network. Boards of Directors join together in networks of corporations. The workings of the body's cells are dictated by a metabolic network of chemical reactions. In recent years, sociologists, physicists, biologists, and others have learned how to probe these networks and uncover their structures, shedding light on the inner workings of systems ranging from bacteria to the whole of human society. This lecture looks at some new discoveries regarding networks, how these discoveries were made, and what they tell us about the way the world works.