Rapid advances in biological sciences are providing many potential molecular targets relevant to human diseases. While genetic approaches often generate valuable tools to evaluate the role of these molecular targets in cellular processes, organism functionality and human disease, small organic molecules represent valuable orthogonal reagents permitting the interrogation of cellular processes. Revolutionary developments in molecular biology, cell biology, robotic-based High Throughput Screening, and informatics enable investigators to probe for ligands that precisely perturb the networks or processes relevant to human diseases. Developments in synthetic chemistry, including combinatorial chemistry and High Throughput diversity oriented synthesis, greatly accelerate access to potential ligands, and modern molecular genetics facilitates the creation of "smart assays" suitable for ligand analyses. These small molecules can provide unique leads for the generation of compounds targeted for drug development using techniques from synthetic and computational chemistry, structural biology, pharmaceutical sciences, and pharmacology. The National Institutes of Health has established a Molecular Library Screening Center Network (MLSCN) to provide the public sector with access to a network of laboratories capable of implementing robust, scalable, and sensitive assays for a broad array of disease-relevant target processes. The mission of the Pittsburgh Molecular Library Screening Center (PMLSC), which was established in July 2006, is to assist investigators interested in interrogating small molecule libraries using optical-based High Throughput and High Content assays.