In this thesis, issues pertaining to the dynamics of nanoscale liquid systems, such as nanojets and nanobridges, in vacuum as well as in ambient gaseous conditions, are explored using both extensive molecular dynamics simulations and theoretical analyses. The simulation results serve as ``theoretical experimental data' (together with laboratory experiments when available) for the formulation, implementation, and testing of modified hydrodynamic formulations, including stochastic hydrodynamics. These investigations aim at extending hydrodynamic formulations to the nanoscale regime. In particular, the instability, and breakup of liquid nanobridges and nanojets are addressed in details. As an application of the microscopic hydrodynamics, a heated-nozzle technique to generate and control nanojets is proposed. Both simulations and microscopic hydrodynamic modeling reveal the formation of a ``virtual convergent nozzle', which consists of a narrowing convergent liquid core within a growing evaporative sheath, by the nanojet itself inside the real nozzle. The diameter of the resulting ejected nanojet is much smaller than the diameter of the nozzle. By adjusting the temperature distribution of the real nozzle, the size and shape of the virtual nozzle are changed, which in turn changes the diameter and the direction of the ejected nanojet.