Figure 2B(1). Schematic diagram of nucleosome assembly and structure. Note the tails on the individual histones emerging from the complexes. Specific amino acids in these tails are the targets of chemical modification to execute the histone code [Jenuwein, 2001 #8287;Gardner, 2011 #15399]. By Richard Wheeler (Zephyris), reproduced with Creative Commons rights from Wikipedia.

Gardner, K. E., C. D. Allis, et al. (2011). "Operating on chromatin, a colorful language where context matters." J Mol Biol 409(1): 36-46.

Jenuwein, T. and C. D. Allis (2001). "Translating the histone code." Science 293(5532): 1074-1080.