During the recent decades, space missions (e.g., CHAMP, GOCE, GRACE and Swarm) have been developed by space agencies in Europe and the USA to measure the Earth’s gravity and magnetic fields and their spatio-temporal variations. These successful missions have already provided a wealth of groundbreaking results about the permanent and time-variable gravity and magnetic fields of the Earth. However, more can be learned about the Earth’s structure by combining data of the gravity and magnetic fields, together with Earth’s rotation data routinely measured using space geodesy techniques, as well as with the most up-to-date modelling of the Earth's internal structure. Use in synergy of these global observables and model data represents a unique way to further investigate the physics of the deep Earth's interior. In addition to the well-known correlation between Earth’s rotation and magnetic field observed at interannual and decadal time scales, recent studies have reported unexpected correlation between spatio-temporal changes of the gravity field and magnetic field, also at interannual time scale. These changes may result from processes occurring in the liquid core and at the core-mantle boundary. This book gathers a series of chapters that provide state-of-the art overviews on the gravity field, magnetic field and Earth’s rotation observations, and on their interpretation in terms of the deep Earth’s structure, as well as on core dynamics and processes at the core-mantle boundary.