Toni Litorja is a research chemist in the Sensor Science Division at NIST. Her work interest is in applying radiometric practices to promote SI-traceability of light measurements in optical imaging methods in biomedicine. She is currently involved in establishing a calibration service for very low light emission (sub-picowatt levels) from luminescent molecular tags. These molecular light emissions are used in benchtop instruments for bioassays and in clinical imaging. Her other work activities are optical imaging for non-contact dimensional measurements, and human visual perception of light and color from images.