Epigenetics refers to a gene regulatory mechanism that integrates and coordinates genetic programs and environmental cues. It plays a critical role in various biological phenomena, such as cell fate decision, embryonic development, and cellular homeostasis. At the molecular level, epigenetic regulation is achieved by conformational changes in chromatin, depending on chemical modifications of DNA and histone proteins. Random X-chromosome inactivation in mammalian females is a typical epigenetic phenomenon, which for example gives diversity in coat color pattern of calico cats and tortoiseshell cats, but some environmental stresses, especially those imposed on fetuses and young can result in long-lasting epigenetic mis-regulation of genes and adult diseases. Thus, epigenetics can be viewed as an interface between genetics and environment. Normally, epigenetic modifications are reset when genetic information is transmitted to the next generation: however, some epigenetic changes, especially those induced by environmental stresses, can be heritable through the germline. In this talk, I will summarize the basics of epigenetic gene regulation and discuss some recent progress in epigenetics research.