This image shows preimplantation mouse embryos with the 2 copies of a specific important genomic sequence (enhancer element) lit up based on its epigenetic state – DNA methylation, reflected by the on-and-off of red (tdTomato) or green (GFP) signal on either copy of such enhancer element. The embryos confirmed our reporters’ great potential to enable studies on the dynamics of DNA methylation and its functional consequences in real-time and in vivo instead of taking snapshots based on sequencing profiles.