The Laboratory of Chemical Biology at the KU Leuven works on the development of chemical probes for covalent labeling of proteins, with a particular focus on proteases. Protease biology is very complex, since most proteases are synthesized as inactive zymogens and once activated, are subject to post-translational regulation. We develop and apply tools, such as activity-based probes: molecules that specifically react with active forms of proteases. Their selectivity can be adjusted by the probe structure. We also develop probes for fluorescent imaging, inhibitors for intramembrane proteases, cleavable linkers for identification of the proteins targeted by our probes and proteomics methods to study protease action.