Genetic engineering is the modification of an organism's genome by using biotechnology. It is used to modify genes and to change their genetic trait. There are a number of techniques that are used in genetic engineering, such as gene isolation, gene targeting and regeneration. These techniques are applied in a number of fields including industrial biotechnology and medicine. 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. In this book, using case studies and examples; constant effort has been made to make the understanding of the difficult concepts of genetic engineering as easy and informative as possible, for the readers.