Genetically engineered organisms or genetically modified organisms (GMO) are animals, plants or microorganisms whose DNA has been altered using genetic engineering techniques. They can be classified into categories such as genetically modified crops, genetically modified medicines and genetically modified animals. Genetically modified crops are the crops whose genes have been modified. They are also called transgenic crops. The main objective of developing these crops is to increase the yield and to produce disease-resistant crops. These crops have entered the markets and have become a part of the global food supply chain. However, genetically modified animals are mainly restricted for research purposes. This book outlines the environmental and economic risks and benefits associated with genetically engineered organisms. Some of the diverse topics covered herein address the varied organisms that fall under this category. The book is appropriate for students seeking detailed information in this area as well as for experts.