Within the nucleus of every cell, the genome does not lie flat but folds into elaborate three-dimensional shapes — and researchers have now shown that these shapes carry the memory of parentage itself. A team studying imprinted genes in mouse brain tissue has found that maternal and paternal chromosomes adopt fundamentally different architectures, and that this spatial difference, not merely the sequence of DNA, determines which parental copy of a gene speaks and which remains silent. The discovery reframes genomic imprinting as a problem of molecular geometry, suggesting that the shape of inh