Due to significant technological advances in the past decades, the body of knowledge on the effects and roles of small molecules in living organisms has grown tremendously . At present, we assume the number of entries across all databases to be in the range of hundreds of millions or billions (10 8 -10 9 ) and a large portion of this data has also accumulated in public databases such as ChEMBL or PubChem BioAssay . Still, these numbers are rather small in comparison to 10 33 , a recently reported estimation of the size of the drug like chemical space . However, it should be noted that numerous studies in the past reported numbers both bigger and smaller depending on the definition used . In addition, considering that only 1-2 measured biological activities per compound are available , the characterization of known compounds also needs to be expanded.