Abstract: The spin of a polarized neutron interacts with a sample's unpaired electrons as well as the magnetic field, making it an invaluable tool for the study of magnetism and other properties of matter. Polarized neutron technology is a powerful method for characterizing fundamental and industrial materials such as magnetic materials, strong-correlation systems, nanomaterials, spintronic materials, polymers, and biological substances. The neutron spin is also an indispensable tool for fundamental research in nuclear and particle physics. In this article, we present a brief introduction to current polarized neutron techniques, including the theory and experimental methods, as well as major applications in various fields of research.