"The Highest Resolution Measurements of Cool Stars"

Stars less massive than our Sun are a dominant presence in the Galaxy. Despite this ubiquity, our ability to measure their fundamental properties and understand their physical nature is limited by their intrinsically small sizes and low luminosities. Consequently, the observational underpinnings of stellar models at the low-mass end of the Main Sequence have been largely based on measurements of a few eclipsing binary systems. With increasingly sensitive and innovative instruments, we are now able to measure single and double systems to further test theoretical models --- and the results are surprising. Many low-mass stars are 10-15% larger than stellar evolution models predict. This talk will present the latest research on fundamental properties of low-mass stars with particular emphasis on mass, radius, and temperature. It will focus on the use of long baseline optical interferometry to achieve extremely high resolution (<1 mas) measurements of M-dwarfdiameters. Lastly, I will explore some of the possible reasons for the discrepancy between model predictions and observations.