Peptides hold enormous promise as chemical tools for selective intervention in biology. They can target chemical space distinct from that of small molecules and their chemical diversity provides high specificity and affinity or target binding. Advances in development of target-based screening technologies and complex peptide library synthesis techniques have enabled the efficient development of peptide tools against numerous targets, including ‘difficult’ protein-protein interactions. The talk will provide an overview of our recent work in this area, with a particular focus on the development and the applications of (cyclic) peptides to probe the biological functions of epigenetic protein families involved in modulating and recognising histone post-translational modifications.