Understanding how our living environment works is essentially a study of ecological systems. Ecology is the science of how organisms interact with each other and with their environment, and how such interactions create self-organizing communities and ecosystems. This science touches us all. This Very Short Introduction celebrates the centrality of ecology in our lives. Jaboury Ghazoul explores how ecology has evolved rapidly from natural history to become a predictive science that explains how the natural world works, and which guides environmental policy and management decisions. Drawing on a range of examples, he shows how ecological science can be applied to management and conservation, including the extent to which theory has shaped practice. Ecological science has also shaped social and cultural perspectives on the environment, a process that influences politics of the environment. Ghazoul concludes by considering the future of ecology, particularly in the light of current and future environmental challenges.