This review discusses the potential of Extreme-Mass-Ratio Inspirals (EMRIs) for testing gravity and General Relativity (GR). EMRIs are binary systems with a massive primary and a much less massive secondary, where the dynamics are dominated by gravitational wave emission. These systems are ideal for testing the nature of black holes and alternative theories of gravity, as they allow for precise measurements of the spacetime geometry and the effects of gravitational interactions. The review covers various aspects of EMRIs, including their formation, detectability, and the effects of environmental factors on their dynamics. It also discusses the potential for testing the existence of new fundamental fields and the nature of compact objects. The review highlights the importance of EMRIs for cosmological and multimessenger tests, as well as for testing the predictions of GR and alternative theories of gravity. The review also discusses the challenges of detecting EMRIs with current and future gravitational wave detectors, and the potential for using EMRIs to study the properties of black holes and the behavior of gravity in extreme conditions. The review concludes with a discussion of the future prospects for EMRIs and their potential for revolutionary discoveries in astrophysics, cosmology, and fundamental physics.This review discusses the potential of Extreme-Mass-Ratio Inspirals (EMRIs) for testing gravity and General Relativity (GR). EMRIs are binary systems with a massive primary and a much less massive secondary, where the dynamics are dominated by gravitational wave emission. These systems are ideal for testing the nature of black holes and alternative theories of gravity, as they allow for precise measurements of the spacetime geometry and the effects of gravitational interactions. The review covers various aspects of EMRIs, including their formation, detectability, and the effects of environmental factors on their dynamics. It also discusses the potential for testing the existence of new fundamental fields and the nature of compact objects. The review highlights the importance of EMRIs for cosmological and multimessenger tests, as well as for testing the predictions of GR and alternative theories of gravity. The review also discusses the challenges of detecting EMRIs with current and future gravitational wave detectors, and the potential for using EMRIs to study the properties of black holes and the behavior of gravity in extreme conditions. The review concludes with a discussion of the future prospects for EMRIs and their potential for revolutionary discoveries in astrophysics, cosmology, and fundamental physics.