Chemical studies typically involve measurements of large ensembles of molecules with data representing averages. With respect to enzymes, we now know such average values represent a simplification. Single enzyme molecule assay utilizing ultrasensivitive capillary electrophoresis laser-induced fluorescence instrumentation have demonstrated that individual enzyme molecules are not identical. Individual molecules differ with respect to rate and activation energy of catalysis. My research interests are in the study of the basis and function of the heterogeneity of enzyme molecules and its role within the cell. A second interest is the development of ultrasensitive methods for the analysis of biological molecules, particulary enzymes and proteins.