Chemoproteomic probes (CPPs) have been widely considered as a powerful molecular biological tool that enables the high-throughput discovery of both binding proteins and modes of action for studied compounds, which has been successfully adopted to identify/validate drug targets by mapping compound-protein interactions, screening lead compounds in early drug discovery, optimizing the efficacy/specificity for the identified lead, etc. Chem(Pro)² is unique in systematically providing diverse types of chemoproteomic probes (CPPs, both the covalent and photoaffinity ones) that experimentally label human proteins in living cells.