The book describes the structure, composition and evolution of the Earth, the main geological processes occurring on it, and how some crucial environmental matters that are amply debated in the media (e.g. pollution, greenhouse effect) can be fully understood by placing them in the holistic context of the system Earth as a whole. It provides basic information on a series of key geological issues, from the structure and composition of the Earth to the large-scale processes that characterize our planet, such as rock alteration and sedimentation, magmatism, geomagnetism, seismicity, plate tectonics, cyclical migration of chemical elements through various Earth reservoirs (Geochemical Cycles), and evolution of the planet from Hadean to present. It intends to reach a wide readership, which is interested in our planet and wish to have a general and comprehensive view of its origin, evolution and activity. Potential readership includes undergraduate and advanced undergraduate students in Geology and other scientific disciplines, and any moderately- to well-educated people interested in the surrounding world and eager to gain a basic knowledge of the Earth and to reach an integrated view of how our planet is working.