The role of known histone modifications, such as Lys acetylation and methylation, in transcriptional control and epigenetics is well-established. Now, Dai et al. identify a novel histone mark, Lys 2-hydroxyisobutyrylation (Khib), and find that this modification is highly abundant and evolutionarily conserved in eukaryotic cells. The authors went on to show that Khib and Lys acetylation marks are located at different histone residues and that Khib is found at amino-terminal histone domains, where most Lys acetylation marks exist, but it also occurs more widely throughout the core histone. Interestingly, the distribution of 2-hydroxyisobutyrylated histone 4 at Lys8 (H4K8hib) is associated with transcriptionally active genes during male germ cell differentiation. Together, these results suggest that Khib is a novel regulator of chromatin function.