EU-OPENSCREEN is a not-for-profit European Research Infrastructure Consortium (ERIC) for chemical biology and early drug discovery. We support all stages of a chemical tool development project, including assay adaptation, high-throughput screening, and chemical optimisation of the ‘hit’ compounds. EU-OPENSCREEN operates an open-access database and a unique, common compound collection. Our main library, the European Chemical Biology Library (ECBL), consists of over 100.000 compounds. EU-OPENSCREEN has over 30 affiliated high-throughput screening and chemistry facilities at partner sites in 10 European countries. These partner facilities provide researchers with access to cutting-edge technologies to develop their own tool compounds.