text: Chemical libraries are usually designed by chemists and chemoinformatics scientists and synthesized by organic chemistry and medicinal chemistry. The method of chemical library generation usually depends on the project and there are many factors to consider when using rational methods to select screening compounds. Typically, a range of chemicals is screened against a particular drug target or disease model, and the preliminary "hits", or chemicals that show the desired activity, are re-screened to verify their activity. Once they are qualified as a "hit" by their repeatability and activity, these particular chemicals are registered and analysed. Chemoproteomics is a field of study that incorporates the use of chemical libraries to identify protein targets. Commonalities among the different chemical groups are studied as they are often reflective of a particular chemical subspace. Additional chemistry work may be needed to further optimize the chemical library in the active portion of the subspace. When it is needed, more synthesis is completed to extend out the chemical library in that particular subspace by generating more compounds that are very similar to the original hits. This new selection of compounds within this narrow range are further screened and then taken on to more sophisticated models for further validation in the Drug Discovery Hit to Lead process.