Choosing which animals to include in a book and which to leave out is a difficult task. For the selection of animals in this volume, the initial premise has been to cover the entire animal kingdom and to include such a wide variety of species as to offer us a complete view of this vast world.
The division of the book's contents is based on the most basic classification of animals: invertebrates and vertebrates. From here, the animals have been grouped according to common characteristics. Each animal is given its scientific name, its common name, a beautiful illustration, a table with its taxonomic data, its distribution and habitat, its physical characteristics and a noteworthy curiosity.