You may not notice water in the ground under your feet, but it plays an important role in keeping you alive. Plants draw water from soil into their roots and use it to grow. If there’s not enough, the resulting drought may have impacts that spread across local water supplies, regional agriculture and even international food prices. NASA’s Gravity Recovery and Climate Experiment (GRACE) mission was the first satellite system to directly measure global changes in the water stored underground in the world’s largest aquifers. GRACE Follow-On, scheduled to launch this month, will continue this important task.