Published in last week's Genome Biology, Steve Jacobsen and team performed a genome-wide study to characterize the patterns of mono-, di- and trimethylation of H3K4 (H3K4me1, H3K4me2 and H3K4me3, respectively) in Arabidopsis thaliana. Using chIP-chip, they found, among other things, that all three types of H3K4me are "almost exclusively genic" while two-thirds of Arabidopsis genes have at least one type of H3K4me.