I will discuss results associated with ongoing surveys to measure diameters and temperatures of main sequence stars with long-baseline optical/infrared interferometry. I will demonstrate how such empirical data are used to construct and calibrate less-direct relationships in order to extend our knowledge to a large number of stars. This analysis includes relations linking color-temperature/radius/luminosity, surface brightness, as well as the global physical properties of temperature-radius-luminosity. The data are also used to identify weaknesses in stellar atmosphere and evolutionary modeling as well as provide empirical constraints to aid in the development of new models. I will discuss how observed discrepancies with models compared to observations have implications for the precise characterization of exoplanets.