Chromosomal surfaces are ornamented with a variety of posttranslational modifications of histones, which are required for the regulation of many of the DNA-templated processes. Histone H3 is one of the five main histone proteins involved in the structure of chromatin in eukaryotic cells. Featuring a main globular domain and a long N-terminus tail, H3 is involved with the ‘beads on a string’ structure of the nucleosome. Histone H3 is the most extensively post-translationally modified of the five histones. The term “Histone H3” alone is purposely ambiguous in that it does not distinguish between sequence variants or modification state. Histone H3 is an important protein in the emerging field of epigenetics, where its sequence variants and variable modification states are thought to play a role in the regulation of genes. For example, histone methylation either on their arginine and/or lysine residues, yields a more diverse array of cellular functions.