There are several reviews focused on chemical space. These reviews, summarized in Table , cover, for example, applications to drug discovery and natural products, progress in visualization methods, and approaches to study the chemical space of small organic compounds with emphasis on the use of public resources. However, the review or research papers using the concept of chemical space use different definitions or have a narrow view or particular view of the space. For instance, often refer to organic molecules with molecular weight of approximately 1,000 Da (typically termed in drug discovery projects "small" molecules) . Table . Selected review papers focused on the chemical space of different types of compounds. a