For embryo implantation to be successful and establish a pregnancy, co-ordination of endometrial receptivity and development of a viable embryo is required. In reality, this occurs infrequently as the rate of conception per natural cycle is as low as ~30%. Little is known about the gene regulatory networks (GRN) that govern implantation in humans, but the distinctly different cellular mechanisms for implantation adopted by different species are reasonably well studied. Tracing these differences back in evolution could help us understand how processes and genes which mediate human interstitial implantation have evolved. This will provide insight into the human-specific features of early life development and the environmental pressures that impact healthy ageing. Our current work has identified genes active at the maternal:embryonic interface in which recent evolutionary change has occurred. We now hypothesise that evolutionary history has strongly impacted subpopulations of the trophectoderm (TE), the outermost cell layer of the implanting embryo, which interacts directly with the maternal environment. The components of the resulting interactome are likely to have changed as distinct interfaces have arisen during evolution. The proposed research will address this hypothesis through a systems-level analysis of the effect of TE subpopulations on early maternal:embryonic interactions. This will be achieved by: 1. Generating single cell RNAseq implantation data using organoid and stem cell models, allowing us to characterise the interactome and define the functional associations of distinct cell subpopulations. 2. Performing a multi-level integrated 'omic analysis of embryo implantation combining transcriptomic, chromatin conformation and epigenomic data. 3. Using our integrated model of multi-omic interactions occurring during implantation as a basis to assess the impact of recent human evolution. The identification of the impact of recent evolution on the implantation process will identify pathways with specific functional relevance. This will provide insight into developmental windows of environmental vulnerability in very early life as well as improving understanding of the fundamental biology of implantation.