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Since 1969, the Apollo and Lunokhod missions have deployed Laser Retroreflector Arrays (LRAs), consisting of Cube Corner Retroreflectors (CCRs), on the lunar surface. These devices reflect incident laser light back toward their source, enabling high-precision distance measurements through the technique of Lunar Laser Ranging (LLR). In LLR experiments, short laser pulses are transmitted from Earth-based ground stations to the lunar LRAs, and the round-trip time of flight (ToF) of the reflected signal is measured to determine the Earth–Moon distance with remarkable accuracy. Together with Satellite Laser Ranging (SLR), which applies the same principle to artificial satellites orbiting Earth, LLR represents one of the most precise techniques available for measuring distances within the Earth–Moon system, routinely achieving millimeter-level precision. These measurements have enabled stringent tests of General Relativity, improved our understanding of the Moon's internal structure, and refined the determination of the terrestrial reference frame. A recent example of SLR employed in fundamental physics missions is the proposed Gravitational Universe Exploration with Satellite Tracking (GUEST) mission, that aim to detect gravitational waves (GWs) in the microhertz band. The mission concept is based on two dense, passive spheres covered with cube-corner retroreflectors, deployed in highly eccentric Earth orbits, tracked continuously by the global network of SLR stations over a minimal time of 10 years. The orbits themselves act as resonant detectors of the oscillating gravitational perturbations, with the microhertz sensitivity emerging from the selected orbital parameters.