Most archaea have small basic proteins that are likely to share a common evolutionary ancestor with eukaryotic histones. A recent study by Mattiroli, Bhattacharyya et al. reported the 4 Å crystal structure of an archaeal histone–DNA complex. The authors reported that the DNA is wrapped around an extended polymer composed of three histone homodimers forming a quasi-continuous superhelix ramp that resembled the geometry of eukaryotic nucleosomes. In addition, mutagenesis experiments that targeted histone polymerization indicated that this assembly is important for the regulation of gene expression. Despite the structural similarities shown by archaeal histone–DNA complexes and eukaryotic nucleosomes, archaea were shown to form a greater variety of complexes with a different number of histone homodimers.