In the last twenty years polarized beams of slow neutrons have been used effectively in fundamental research in nuclear physics. Parity violation in nuclear fission and neutron optics was discoverd as well as the nuclear precession of neutrons and the coherent interference of spin channels in neutron capture by nuclei. Furthermore, these methods helped to understand better the neutron`s electric dipole moment and its beta decay. This book gives a thorough introduction to these experimental methods including the most recent techniques of generating and analyzing polarized neutral beams. It clearly shows the close relationship between elementary particle physics and nuclear physics, in particular in the section dealing with the effects caused by weak interactions. Special attention is paid to experiments which investigate the violation of quantum mechanical conservation laws. The book not only addresses specialists but also those interested in the foundations of elementary particle and nuclear physics. It is well suited as additional reading for students.