Reversible modification of histone tails is a regulatory step in chromatin remodeling. The N-terminal tails of histones are signaling platforms that carry amino acid residues for post-translational modification and contribute to chromosomal higher order structure. These modifications are performed by a number of chromatin modulators such as histone (h) acetyltransferase, h-deacetylase, h-methyltransferase and h-kinase. Large numbers of these enzymes as well as other chromatin-associated proteins share the bromodomain, a signature protein motif. Structural studies reveal not only wide structural conservation of bromodomains but also envision a possible role of this domain in the recognition of specific modified residues in the histone tails. The widespread presence of bromodomains in leukemogenic and cancer genes has provided a fundamental tool for studies of the role of epigenetic and chromatin remodeling in malignant diseases.