Molecular imaging is leading an important role in the era of molecular medicine. Optical imaging, a rising star in the filed of molecular imaging, largely consists of bioluminescent imaging and fluorescent imaging. It has been shown that well-aimed and creatively-built optical-imaging-reporters let researchers explore and answer a lot of biologically important questions in living subjects. Despite relatively short history, molecular optical imaging is rapidly being implemented not only in many clinical areas but also in various research fields from tracking gene expression, protein-protein interaction or migrating cells to molecular diagnosis and treatment. J Korean Neurol Assoc 24(2):101-105, 2006