Electron Cyclotron Resonance (ECR) is a phenomenon that occurs when charged particles, like electrons, move in a magnetic field. As these particles spiral around the magnetic field lines, they can absorb energy from an electromagnetic wave at a specific frequency. This frequency is directly related to the strength of the magnetic field and the mass of the particles. ECR is commonly used in various applications, including plasma physics and fusion research. By harnessing this resonance, scientists can efficiently heat and control plasmas, which are essential for experiments aimed at achieving controlled nuclear fusion, a potential source of clean energy.