Mammalian genomes are not equivalent due to parental-origin-specific epigenetic modifications, which allows embryos to develop to term via monoallelic gene expression.The phenomenon is called as genomic imprinting. The paper picked up reports the involvement of DNA methylation in genomic imprinting. In this lecture, we will try to realize the importance of the link between a biological phenomenon and its molecular nature by regarding the paper as a "figure or key data" of the "article" of genomic imprinting. Hence, we will discuss the influence of the paper in later study.