Gravity plays a significant role in both life and physical science processes. In life sciences, at the level of a whole organism, gravity as unit gravity on Earth (9.81 ms−2), the lack of gravity during free fall, or the increase of gravity while, e.g., during centrifugation is reflected in an organism’s metabolism, anatomy, and behavior. In this chapter, the impact of near weightlessness and hypo- and hypergravity on animals related to buoyancy, sedimentation, and hydrostatic pressure will be addressed. It will provide a concise historical overview of these processes for in-flight and ground-based studies on animals and the experimental modalities that have been or could be used in future investigations.