We have given ourselves the assignment of trying to write a book about places everyone sees, but no-one knows. In completing the work, we have tried to keep a number of things in mind. First, we recognize that readers have an insatiable curiosity for the truth, and within the context of natural history and ecology this is especially true because the answers to questions about non-human taxa sometimes help us interpret the significance of Homo to the world. This can comfort us. Second, we acknowledge the message that ‘complex questions have simple, easy to understand, wrong answers’. Thus, the kinds of simple questions we ask may not provide simple answers, and in the work that follows we will try to simplify only when such efforts can provide reasonably precise and accurate versions of the truth. Given that this is the first book on the topic of cliff ecology, it may also happen that certain topics have been so understudied that no effective summaries or syntheses can be made. When problems like this are encountered, we will try to bring them to the reader's attention. Lastly, we will try not to misrepresent to the reader the source of the motivation for doing science in general, and cliff ecology in particular – we love cliffs. Sometimes in the writing of science these motivations become lost in the intricacies of logic. You all know the wording: ‘In order to test whether species packing densities could be predicted from the equilibrium theory of island biogeography we sampled …’ which translates into English as ‘islands are fascinating.’