The animal world is immensely diverse, and our understanding of it has been greatly enhanced by analysis of DNA and the study of evolution and development ('evo-devo'). In this Very Short Introduction Peter Holland presents a modern tour of the animal kingdom. Beginning with the definition of animals (not obvious in biological terms), he takes the reader through the high-level groupings of animals (phyla) and new views on their evolutionary relationships based on molecular data, together with an overview of the biology of each group of animals. The phylogenetic view is central to zoology today and the volume will be of great value to all students of the life sciences, as well as providing a concise summary for the interested general reader.