The establishment of epigenetic modifications (imprints) during gametogenesis, and propagation of these imprints during the organism's life. Genomic imprinting leads to an asymmetry between the maternal and paternal alleles and differential expression of the corresponding alleles. This can happen through heterochromatin formation or differential chromatin loop formation. [ http://www.ncbi.nlm.nih.gov/pubmed/24492710 http://www.ncbi.nlm.nih.gov/pubmed/31965998 http://www.ncbi.nlm.nih.gov/pubmed/31896690 ]