Cliffs are present in virtually every country on earth. The lack of scientific interest in cliffs to date is in striking contrast to the commonness of cliffs around the world and to the attraction cliffs have had for humans throughout history. Cliffs provide a unique habitat, rarely investigated from an ecological viewpoint. This book aims to destroy the impression of cliffs as geological structures devoid of life, by reviewing information about the geology, geomorphology, microclimate, flora, and fauna of both sea and inland cliffs. For the first time, evidence is presented to suggest that cliffs worldwide may represent an invaluable type of ecosystem, consisting of some of the least disturbed habitats on earth and contributing more to the biodiversity of a region than their surface coverage would indicate.