This book presents the fundamental ideas and facts about the Bacillus thuringiensis and its largest Cry1 insecticidal crystal proteins. It has got its shape because of growing usage of Cry toxins in the agriculture field. It was written keeping in the mind the beginning graduates and the readers who are new to the field of Bacillus thuringiensis based research. These two made us to keep the book in compact and concise manner and give more information in tabular form so that it will be easily to grasp and convey more to the audience. In this handbook we arranged topics in logical progression. It starts with a basic knowledge about the Bacillus thuringiensis, its isolation and identification process and takes a reader upto Bt based genetically modified crops and the countries which have approved these in any form. Threats faced by Bt toxins based technology have also been discussed. We hope this book will serve a handy for the reader to grasp the gifts given by Bt based technology.We assume it will stimulate the reader to refer the further literature. We have given the major references at the end which served as a back bone for the creation of this book.