Two of the most challenging problems at the intersection of electronic structure theory and molecular dynamics simulations are the accurate representation of intermolecular interactions and the development of  reduced-scaling algorithms applicable to large systems. To some extent, these two problems are antithetical, since the accurate calculation of non-covalent interactions typically requires correlated, post-Hartree-Fock methods whose computational scaling with respect to system size precludes the application of these methods to large systems. I will describe our many-body molecular dynamics (MB-MD) methodology for aqueous systems that overcomes these limitations and enables computer simulations from the gas to the condensed phase, with chemical and spectroscopic accuracy. MB-MD is a unified molecular dynamics framework that combines many-body representations for potential energy, dipole moment, and polarizability surfaces, derived entirely from correlated electronic structure data using supervised learning techniques, with quantum dynamics methods that explicitly account for nuclear quantum effects. I will discuss the accuracy and predictive ability of the MB- MD methodology in the context of molecular modeling of complex systems, including solutions, interfaces, and porous materials, with a particular focus on the relationships between structural/dynamical properties and vibrational spectra.