Unsupervised clustering of fetal tissues demonstrates that each tissue has a distinct DNA methylation profile. Sample names are shown with labelling of the corresponding tissue types. Tissue samples were clustered by hierarchical clustering of β values based on the formula 1-r (Beadstudio software; Illumina), where r is the correlation coefficient between samples. Specific tissue types clustered together, with strong correlation between samples derived from the same tissue. All tissues had distinct clustering from the other groups, except for one muscle sample from T21 (FT1_t21_muscle), which clustered with the skin sample from the same fetus.