While the main causes of the temporal gravity variations observed by the GRACE space mission result from water mass redistributions occurring at the surface of the Earth in response to climatic and anthropogenic forcings (e.g., changes in land hydrology, in ocean mass, in mass of glaciers and ice sheets), solid Earth's mass redistributions are also recorded by these observations. This is the case, in particular, for the Glacial Isostatic Adjustment (GIA) or the viscous response of the mantle to the last deglaciation. However, it is only recently showed that the gravity data also contain the signature of flows inside the outer core and their effects on the core-mantle boundary (CMB). Detecting deep Earth's processes in GRACE observations offers an exciting opportunity to provide additional insight on the dynamics of the core-mantle interface. Here, we present one aspect of the GRACEFUL (GRavimetry, mAgnetism and CorE Flow) project, i.e. the possibility to use the gravity field data for understanding the dynamic processes inside the fluid core and core-mantle boundary of the Earth, beside that offered by the geomagnetic field variations.