Taming the transposon: H3K9me3 turns foe to friend in human development

In this issue of Cell Stem Cell, Xu et al. and Yu et al. use low-input epigenetic profiling techniques to map H3K9me3 deposition in early human development. They reveal stage-specific H3K9me3 deposition on retrotransposons, which may play crucial cis-regulatory roles in early development.