Laser interferometry is the most precise technology available for measuring distance changes between both close and distant objects, e.g. test masses in gravitational physics and distant satellites. Both were successfully demonstrated for the first time in the LISA Pathfinder Mission and the GRACE Follow-On Mission, both with central contributions from Hannover. The respective applications are the measurement of gravitational waves and the measurement of the Earth's gravitational field for climate research. Following these successful initial demonstrations, laser interferometry is now being further developed for the next generation of satellites. In addition, the development of miniaturized laser interferometric inertial sensors also represents an extremely promising alternative to classical accelerometers and gyroscopes.