The study of the changes in the heritable phenotypes, which do not involve any alterations in the DNA sequence, is known as epigenetics. It usually denotes the changes which affect gene activity and expression. It can also be used to describe heritable phenotypic changes. The effects on the physiological and cellular phenotypic traits often result from external or environmental factors. Epigenetics has several medical applications. It plays a major role in congenital genetic diseases such as Prader-Willi syndrome and Angelman syndrome. The study of epigenetic modifications to the DNA of cancer cells, which do not involve a change in the nucleotide sequence, is called cancer epigenetics. The ever-growing need of advanced technology is the reason that has fueled the research in the field of clinical epigenetics in recent times. The objective of this book is to give a general view of the different areas of clinical epigenetics and their applications. As this field is emerging at a rapid pace, the contents of this book will help the readers understand the modern concepts and applications of the subject.