The Cairns lab has made many contributions to understanding chromatin structure and gene expression principles in the germline – which include: 1) The first genome-wide analyses of histone retention and modifications in human sperm, revealing the retention in mature sperm of differentially-modified histones enriched at the promoters of developmental and housekeeping genes. 2) Evidence that pluripotency network genes are silenced in spermatogonia by chromatin and DNA, and the surprising result that gametogenesis in mice and humans involves the transcription of hundreds of genes bearing DNA methylation and co-incident H3K4me3 (Hammoud et al., Cell Stem Cell, 2014).