DNA methylation is a process by which a methyl group is added to the DNA molecule, typically at cytosine bases within the DNA sequence. This modification can regulate gene expression by altering the accessibility of the DNA to transcription factors and other proteins involved in gene regulation. DNA methylation plays a crucial role in many biological processes, including embryonic development, genomic imprinting, and X-chromosome inactivation. Aberrant DNA methylation patterns have been associated with various diseases, including cancer and neurological disorders. Studying DNA methylation can provide valuable insights into the mechanisms of gene regulation and disease development.