Electron Paramagnetic Resonance (EPR) is a spectroscopic technique used to study materials with unpaired electrons. It detects the magnetic fields around these electrons, providing insights into their environment and interactions. EPR is particularly useful for analyzing free radicals, transition metal complexes, and defects in solids. The technique involves applying a magnetic field to a sample and exposing it to microwave radiation. When the energy levels of the unpaired electrons align with the microwave frequency, resonance occurs, allowing researchers to gather information about the electronic structure and dynamics of the sample.