In addition to the ultrasensitive quantitative assay, our lab is also interested in studying single molecule enzymology utilizing the microwell array platform. The single-molecule enzymology could demonstrate the divergent activity of individual enzymes and thus convey more kinetic information than bulk assay. The microarray contains more than 200,000 micrometer sized wells. When loaded with sufficiently low concentrations of enzyme solutions, each microwell will have either one or zero enzyme molecules based on Poisson distribution. Therefore, hundreds of single enzyme molecules can be monitored simultaneously. Compared with other competing techniques such as flow cytometry, that can only monitor end-point signal intensity, aqueous solutions can be kept inside the microwells for several hours without any leaking, allowing the microscope to record signal changes over a long period and thereby derive the kinetic properties of the enzyme.