With the development of high throughput screening (HTS) during the last two decades new technologies have gained access to chemistry and biology laboratories. The use of both, laboratory robotics and automated workstations has greatly increased the number of chemical entities that are synthesized for and tested against new targets. While a decade ago a daily throughput of about 1,000 compounds was considered sufficient, nowadays screening laboratories aim to achieve 100 times as many samples in the same period of time. Combinatorial chemistry vice versa has increased comparably the daily output and HTS has become an important success factor during early lead finding. Nearly all drug discovery research projects in pharmaceutical industry employ HTS screening assays as initial steps to discover the chemical leads. These compounds provide the structural basis for further medicinal chemistry activities that focuses on optimization of the lead with respect to the activity and selectivity profile in order to identify the development candidate.