The process via which methyl groups are added to the DNA molecule is known as DNA methylation. It is a process that can change the activity of a DNA segment without changing the sequence. DNA methylation is commonly found in three different sequences CG (or CPG), CHG (or CHH) and CpApC in plants and other organisms. In human beings and animals, DNA methylation happens mainly at the C5 position of CpG dinucleotides. It is carried out by maintenance methylation and de novo methylation that are the two common classes of enzymatic activities. Wherein DNA methylation in plants happens in CpG, CpHpG, and CpHpH sites, where H represents any nucleotide and there is no representation of guanine. This book is a compilation of chapters that discuss the most vital concepts and applications in the field of DNA methylation. Different approaches, evaluations, methodologies and advanced studies on DNA methylation have been included herein. It is a resource guide for experts as well as students.