The Histone H3 human monoclonal antibody, clone 1G1, recognizes human Histone H3. This protein is one of the five main histone proteins involved in the structure of chromatin in eukaryotic cells. Histones are basic nuclear proteins that are responsible for the nucleosome structure of the chromosomal fiber in eukaryotes. Histone variants have emerged as important contributors to the regulation of chromatin structure and therefore of almost all DNA-based processes. Hence, these specialized proteins play important roles in transcriptional regulation, cell cycle progression, DNA repair, chromatin stability, chromosome segregation and apoptosis. Due to their evident biological significance, it is not surprising that mutations or the deregulation of their expression levels can have severe implications for cellular functions that ultimately might contribute to or even drive disease development, most notably cancer. Besides the histones themselves, their respective chaperone/remodeling complexes needed for precise variant chromatin deposition, are consequently frequent targets in neoplasms and diverse diseases.