Optical atomic clocks are exemplary quantum sensors, combining robust environmental decoupling with exquisite laser phase sensitivity. By leveraging new quantum engineering techniques, today’s optical clocks now realize a staggering 19 digits of accuracy and precision. Beyond timekeeping, this new level of performance promises novel tests of fundamental physics, from general relativity to dark matter. Motivated by these advances, I will show how carefully controlling ensembles of neutral atoms tightly confined within optical lattices continues to push the limits of frequency metrology. I will first introduce optical lattice clocks (OLCs), which set precision records by leveraging thousands of trapped alkaline-earth-like atoms. Using strontium in a shallow lattice regime allows us to control atomic interactions and realize unprecedented measurement capability, resolving the gravitational redshift within our millimeter-scale atomic sample. In ytterbium we have developed and employed multiple ultracold ensembles within a standard OLC to measure accuracy-limiting differential atomic polarizabilities. Recently we have even operated OLCs outside the lab, with plans for measuring gravitational redshifts atop nearby mountains. Looking forward, the OLC architecture can be extended beyond alkaline-earth-like atoms, enabling a single-species clock network to explore new frontiers in both quantum metrology and fundamental physics.