The use of epigenome editing is set to expand our knowledge of how epigenetic landscapes facilitate gene expression capacity within a given cell. As epigenetic landscape profiling in health and disease becomes more commonplace, so does the requirement to assess the functional impact that particular regulatory domains and DNA methylation profiles have upon gene expression capacity. That functional assessment is particularly pertinent when analysing epigenomes in disease states where the reversible nature of histone and DNA modification might yield plausible therapeutic targets. In this review we discuss first the nature of the epigenetic landscape, secondly the types of factors that deposit and erase the various modifications, consider how modifications transduce their signals, and lastly address current tools for experimental epigenome editing with particular emphasis on the immune system.