The term “epigenetics” refers to the study of modifications that do not alter the sequence of DNA, but which can directly influence gene expression. Epigenetic mechanisms include DNA methylation, histone modifications, and non-coding RNAs, such as microRNAs (miRNAs). DNA methylation plays a crucial role in various developmental processes. It helps to maintain genome stability by silencing repetitive elements and regulates tissue-specific and developmental stage-specific gene expression during cell division. Histone tail modifications can alter chromatin architecture and regulate gene expression by opening and closing chromatin structure. MiRNAs are short regulatory RNAs that inhibit post-transcriptional gene expression by either suppressing the translation of their target mRNAs or causing mRNA degradation. Environmental factors have been found to modulate in many cases epigenetic marks, contributing to the onset of multiple human pathologies. Therefore, epigenetic modifications are increasingly considered as potential biomarkers for the early diagnosis and prognosis of human diseases.