Neutron spin echo spectroscopy allows the observation of long range internal relaxation mechanisms of macromolecules, simultaneously in space and time. Thereby, it facilitates a microscopic study of the molecular origins of the macroscopic viscoelastic properties of polymer materials. The molecular understanding of polymer dynamics bases on concepts of entropic forces and topological and hydrodynamic interactions. I shall briefly outline the different concepts and then discuss experimental results on these different aspects of polymer motion on a molecular scale.