Indeed, in epigenetic drug discovery, there are recent and increased efforts to design and analyze focused libraries. By design, epigenetic-focused libraries have the potential to increase the epigenetic relevant chemical space, which has recently been revised. Depending on the library developer, the compounds in the compound data sets are selected following a multi-step procedure, typically through computational approaches (although the specific methodological details remain undisclosed to the public). Many providers emphasize the diversity of the libraries, yet it remains hidden to the user what their contents and coverage of the chemical space are.