The quality of a chemical library significantly impacts drug discovery success. The paper titled "MBC and ECBL libraries: outstanding tools for drug discovery" has been published with the collaborative efforts of scientists Ana Martinez and Carmen Gil from the EU-OPENSCREEN medicinal chemistry partner site Centro de Investigaciones Biológicas “Margarita Salas” (CIB-CSIC) in Spain. Results of this analysis remark the high quality in terms of structural diversity and drug-like properties of the Medicinal and Biological Chemistry (MBC) and the EU-OPENSCREEN European Chemical Biology library (ECBL), making them great reservoirs of hits for drug discovery. The paper can be downloaded here: https://www.frontiersin.org/articles/10.3389/fphar.2023.1244317/full