At UCSF, he built microscopy systems for studying cellular sub-structure, making use of a variety of new technologies to improve imaging at the nanoscale in biomedicine and engineering. He built the first structured illumination microscope (SIM) fast enough to image living cells, working with Mats Gustafsson, a leader in the field of high-resolution microscopy. Besides teaching and mentoring students at UGA, Peter is developing a new microscope that will use a variety of techniques to measure and correct optical aberrations for in vivofluorescence imaging.