Network science is the study of networks, which are systems of interconnected data points, also known as nodes, and the edges that connect them to each other. It includes techniques for analyzing the patterns and configuration of nodes and edges as well as how these configurations relate to properties of nodes. Some of our recent work includes analyzing sexual partner networks, substance use networks, confidant networks and online social networks of populations at increased risk of morbidity and mortality from HIV. Directly observing how individuals are connected allows us to examine how they potentially influence each other, what factors are related to their connections, and how interventions work in networks. This enables us to examine how real-world interventions may impact the larger population beyond those receiving an intervention.