New tools for probing complex interfaces have been developed and applied to a variety of systems. Deep UV second harmonic generation and electronic sum frequency generation, soft X-ray second harmonic generation, and X-ray spectroscopy of liquid microjets have been employed to characterize the behavior of ions at air/water and graphene/water interfaces. New insights have been realized for the behavior of carbonates at electrolyte interfaces, which may impact our understanding of the carbon cycle.