The quantum mechanical properties of small molecules provide the basis for our quantitative understanding of chemistry and a testing ground for new theories of molecular structure and reactivity. With modern methods, small molecular systems can be investigated in extraordinary detail by high-resolution spectroscopic techniques in the frequency or the time domains, and by complementary theoretical and computational advances. This combination of cutting-edge approaches provides rigorous tests of our understanding of quantum phenomena in chemistry. The chemical properties of small molecules continue to present rich challenges at the chemistry/physics interface since these molecules exhibit properties in isolation, and interact with their environments, in ways that are not yet fully understood. The coupled electronic and nuclear motions may lead to complex structural or dynamical features that can now be observed experimentally. From a theoretical point of view, these features can only be explained if the quantum nature of the atomic nuclei is considered together with the possible couplings between nuclear and electronic degrees of freedom. New developments, from both the theoretical and experimental side, are urgently needed if the properties of small molecules are to be optimally exploited in future technological, engineering and biological applications of outstanding importance. This Faraday Discussion will address the quantum dynamical properties of small molecules, both in isolation where extraordinarily detailed and precise measurements and calculations are now emerging, and when embedded in complex media such as molecular clusters, quantum fluids and bulk liquids. The Discussion will appeal to researchers working on both isolated and confined molecular systems. This volume covers four main themes:Precise Characterisation of Isolated MoleculesQuantum Dynamics of Isolated MoleculesMolecules in Confinement in Liquid SolventsMolecules in Confinement in Clusters, Quantum Solvents and Matrices