Ever since its discovery a century ago, superfluid helium has proven invaluable in testing the laws of modern quantum mechanics. Superfluidity can indeed be shown to arise from the long-range atomic phase coherence associated with the Bose-Einstein condensation (BEC) but also from the existence of well-defined characteristic collective modes within the liquid. This renowned BEC theory of superfluidity (originally proposed by F. London) and the celebrated phonons theory (proposed by L. Landau) were thought to be opposing and based on conflicting physical pictures. In this talk, I will first introduce the concept of neutron spectroscopy, and show how over the course of a few years we combine it with other measurement techniques to conclusively demonstrate that the long-range phase coherence and modes both arise from BEC, effectively reconciling the two theories. Finally, using a more general example, I will discuss how neutron spectroscopy can be used to benchmark the molecular dynamics and vibrations in polymeric materials, such as poly(p-phenylene vinylene) derived compounds.