Optical pumping is a technique used in the field of optics and quantum mechanics to manipulate the state of atoms or particles using light. By shining laser light on a sample of atoms, researchers can excite the electrons within the atoms to higher energy levels, effectively "pumping" energy into the system. This process can be used to control the spin orientation of particles, study the dynamics of atomic and molecular systems, and create coherent sources of light for applications in quantum computing and communications. Optical pumping has a wide range of practical applications, including in the development of atomic clocks, magnetometers, and atomic vapor cells for quantum information processing.