Ecological systems are undeniably complex, including many species interacting in different ways with each other (e.g., predation, competition, facilitation, parasitism). One way of visualizing, describing, and studying this complexity is to represent them as networks, where nodes are typically species and links are interactions between these species. The study of these networks allows understanding of the rules governing the topology of their links, and assessing how network structure drives ecological dynamics. Studies on different types of ecological networks have suggested that they exhibit structural regularities, which in turn affect network dynamics and resilience to perturbations. Although the use of networks to represent ecological communities dates back to the early stages of the discipline, the last two decades have seen rapid progresses in our understanding of ecological networks, as data are collected at a faster rate and better resolution, as metrics are continuously developed to better characterize network structure and as numerical simulations of mathematical models have allowed investigating how network structure and dynamics are related in more comprehensive and realistic ecological networks. This chapter describes some of the recent developments and challenges related to the study of ecological networks. After defining networks in general, and ecological networks more specifically, recent results regarding the structure of different types of ecological networks, and what is known about their dynamics and resilience, are presented.