This book is an introductory overview on a rapidly evolving scientific discipline of Geobiology. It studies Earth from both geological and biological perspective. This book covers the many facets of this research field, and underlines its potential for the exploration of the definition of life, the co-evolution of life and Earth, the appreciation of global environmental problems, and the detection of life in the universe. The book serves the advanced reader as compass for future studies, and as guideline for instruction.