A compound library or chemical library from TargetMol is a collection of stored chemicals usually used ultimately in high-throughput screening or industrial manufacture. Depending upon their scope (specific goal or diverse oriented goal) and design (chemical space or scaffold), our compound libraries can be classified as Focused Bioactive Libraries, Natural Product Libraries, Fragment Libraries, and Diversity Sets. These libraries have been extensively validated in our in- house biological assays and widely employed by research institutions and pharmaceutical companies in complementary screening strategies. Identifying novel and robust chemical starting points remains one of the biggest challenges in drug discovery today. Over the last decade, it has been common practice during the early stage of a project to screen vast numbers of compounds that cover larger section of chemical space evenly (diversity-led paradigm) in high-throughput assays in order to identify those chemicals which have the potential to modulate the target of interest. The costly nature of such mass screening, the consequent need to use reductionist assays that are optimized primarily for scale and speed, and the increasing realization that drug property space is far from random has more recently led to the use of smaller, higher quality screening collections (target-led approaches). All of these compound libraries and their screening approaches have their own particular advantages and disadvantages.