Epigenetic differences arise during the lifetime of monozygotic twins. Despite sharing the same genotype, monozygotic twins often exhibit phenotypic differences, such as disease susceptibility and anthropometric traits. This study investigated global and locus-specific differences in DNA methylation and histone acetylation in a large cohort of monozygotic twins. The results showed that while young twins are epigenetically similar, older twins display significant differences in 5-methylcytosine DNA and histone acetylation, affecting gene expression. These findings suggest that epigenetic differences contribute to phenotypic variation in genetically identical individuals. The study analyzed DNA methylation, histone acetylation, and gene expression in monozygotic twins of different ages. Epigenetic differences were observed in various tissues, including lymphocytes, epithelial cells, and skeletal muscle. These differences were associated with lifestyle factors, environmental influences, and the duration of shared living. The results indicate that epigenetic modifications can vary significantly between twins, even when they share the same genetic makeup. The study also found that epigenetic differences are more pronounced in older twins, who have different lifestyles and less shared history. These differences were linked to changes in gene expression, with older twins showing more distinct expression profiles. The findings highlight the role of epigenetic factors in explaining phenotypic differences among monozygotic twins and suggest that epigenetic changes may contribute to the development of diseases in these individuals. The study used various techniques, including AIMS, bisulfite genomic sequencing, and comparative genomic hybridization, to identify epigenetic differences. These methods revealed that epigenetic modifications can occur in different regions of the genome, affecting gene expression and contributing to phenotypic variation. The results support the idea that epigenetic factors play a crucial role in determining phenotypic outcomes, even in genetically identical individuals. The study underscores the importance of considering epigenetic differences in understanding the development of diseases and phenotypic variation in monozygotic twins.Epigenetic differences arise during the lifetime of monozygotic twins. Despite sharing the same genotype, monozygotic twins often exhibit phenotypic differences, such as disease susceptibility and anthropometric traits. This study investigated global and locus-specific differences in DNA methylation and histone acetylation in a large cohort of monozygotic twins. The results showed that while young twins are epigenetically similar, older twins display significant differences in 5-methylcytosine DNA and histone acetylation, affecting gene expression. These findings suggest that epigenetic differences contribute to phenotypic variation in genetically identical individuals. The study analyzed DNA methylation, histone acetylation, and gene expression in monozygotic twins of different ages. Epigenetic differences were observed in various tissues, including lymphocytes, epithelial cells, and skeletal muscle. These differences were associated with lifestyle factors, environmental influences, and the duration of shared living. The results indicate that epigenetic modifications can vary significantly between twins, even when they share the same genetic makeup. The study also found that epigenetic differences are more pronounced in older twins, who have different lifestyles and less shared history. These differences were linked to changes in gene expression, with older twins showing more distinct expression profiles. The findings highlight the role of epigenetic factors in explaining phenotypic differences among monozygotic twins and suggest that epigenetic changes may contribute to the development of diseases in these individuals. The study used various techniques, including AIMS, bisulfite genomic sequencing, and comparative genomic hybridization, to identify epigenetic differences. These methods revealed that epigenetic modifications can occur in different regions of the genome, affecting gene expression and contributing to phenotypic variation. The results support the idea that epigenetic factors play a crucial role in determining phenotypic outcomes, even in genetically identical individuals. The study underscores the importance of considering epigenetic differences in understanding the development of diseases and phenotypic variation in monozygotic twins.