Most people can readily identify a forest, or a grassland, or a wetland - these are the simple labels we give different plant communities. The aim of this book is to move beyond these simple descriptions to investigate the 'hidden' structure of vegetation, asking questions such as how do species in a community persist over time? What prevents the strongest species from taking over? And, are there rules that confer stability and produce repeatable patterns? Answers to these questions are fundamental to community ecology, and for the successful management of the world's varied ecosystems, many of which are currently under threat. In addition to reviewing and synthesising our current knowledge of species interactions and community assembly, this book also seeks to offer a different viewpoint - to challenge the reader, and to stimulate ecologists to think differently about plant communities and the processes that shape them.