Density functional theory (DFT) has emerged as the most widely utilized quantum mechanical (or first-principles based) computational methodology for investigating the structure, stability, and function of a wide variety of systems throughout the fields of chemistry, physics, and materials science. In this talk, I will demonstrate how novel theoretical and algorithmic developments, coupled with an efficient utilization of massively parallel supercomputer architectures, enable us to perform large-scale and systematically-improvable DFT calculations on realistic molecules and materials in the condensed phase (e.g., solids and liquids). Illustrative examples will include the microscopic structure and equilibrium density of ambient liquid water, the quintessential condensed-phase molecular systems of interest.