Observing the interactions of cells with materials requires the spatial and temporal resolution provided by fluorescence microscopy. While recent developments in fluorescence microscopy make it possible to image many of the dynamic events that are essential to cellular function, new methods are necessary to observe the dynamics of single molecules inside living cells. Imaging within live cells is difficult as the emission from fluorescent probes competes with the autofluorescence of the cell. The Payne Lab is developing new optical techniques for quantitative cellular imaging. Optical methods of interest include nanometer-level imaging, spectroscopic single-particle tracking, and multiphoton total internal reflection microscopy.