Adult and Foetal hearts were integrated using R Seurat's reciprocal principal component analysis (RPCA) pipeline. This dataset contains single-cell RNA sequencing from 7 foetal hearts between the ages of 8 and 11 weeks post-conception dissected into either base or apex. Foetal data were combined with similar data from multiple regions from 6 adult hearts, including single nuclei (Heart Cell Atlas). This dataset contains a sub-sampled and balanced composition of cell types as described in the materials and methods of the article. Raw data is available from GEO using the accession ID GSE216019.