Genomic imprinting is an epigenetic mechanism in mammals that restricts the expression of a subset of genes to one parental chromosome, resulting in monoallelic, parental-specific gene expression. This phenomenon affects a few hundred genes out of the approximately 25,000 genes in the mammalian genome, primarily influencing embryonic and neonatal growth. Imprinted genes are epigenetically marked in gametes through DNA methylation at imprinting control elements (ICEs), which are then inherited and maintained in the embryo. The expression of imprinted genes is regulated by long noncoding RNAs (lncRNAs), histone modifications, insulators, and higher-order chromatin structure. These mechanisms ensure that imprints are maintained after fertilization despite extensive genome reprogramming. Genomic imprinting is crucial for understanding mammalian epigenetic regulation and has implications for medical, societal, and intellectual aspects, including genetic disease management, breeding control, and biotechnology. The evolution of genomic imprinting is thought to have occurred independently multiple times, possibly in response to parental conflict or trophoblast defense mechanisms. Imprinted gene clusters, often containing multiple protein-coding mRNAs and at least one lncRNA, are regulated by ICEs that carry epigenetic imprints inherited from one parental gamete. DNA methylation plays a key role in establishing and maintaining these imprints, acting as a cis-acting mechanism to control gene expression.Genomic imprinting is an epigenetic mechanism in mammals that restricts the expression of a subset of genes to one parental chromosome, resulting in monoallelic, parental-specific gene expression. This phenomenon affects a few hundred genes out of the approximately 25,000 genes in the mammalian genome, primarily influencing embryonic and neonatal growth. Imprinted genes are epigenetically marked in gametes through DNA methylation at imprinting control elements (ICEs), which are then inherited and maintained in the embryo. The expression of imprinted genes is regulated by long noncoding RNAs (lncRNAs), histone modifications, insulators, and higher-order chromatin structure. These mechanisms ensure that imprints are maintained after fertilization despite extensive genome reprogramming. Genomic imprinting is crucial for understanding mammalian epigenetic regulation and has implications for medical, societal, and intellectual aspects, including genetic disease management, breeding control, and biotechnology. The evolution of genomic imprinting is thought to have occurred independently multiple times, possibly in response to parental conflict or trophoblast defense mechanisms. Imprinted gene clusters, often containing multiple protein-coding mRNAs and at least one lncRNA, are regulated by ICEs that carry epigenetic imprints inherited from one parental gamete. DNA methylation plays a key role in establishing and maintaining these imprints, acting as a cis-acting mechanism to control gene expression.