Epigenesis is defined as heritable changes that can modulate gene expression without any changes in DNA sequence, including reversible modification of DNA and chromatin and post-transcriptional regulation. DNA methylation, histone modification and non-coding RNA regulation are the 3 pillars of epigenetics research. These epigenetic mechanisms play important roles in developmental regulation, the response to biotic and abiotic stress, and environmental adaption of plants. This review covers the research into epigenetic modifications in plants and impact on the developmental process of plants (e.g., plant height, flowering time, floral symmetry, fruit ripening) and the response of plants to environmental stresses.