All eukaryotes organize their genomes in the form of chromatin, acomplex of DNA and dedicated packing proteins, so-called histones.In addition to compacting DNA, chromatin regulates the activity of encodedgenes through posttranslational modifications of the histone proteins. Deciphering the complex crosstalk between histone modificationsand gene activity represents a central challenge for biomedical science.Our group is developing and using chemical tools to study thephysiological function of posttranslational histone modifications. To this end we combine methods from chemistry, biochemistryand molecular biology to probe a wide range of chromatin factors including chromatin binding proteins and histone-modifying enzymes.