Over the last few decades, various techniques have been developed to alter the properties of plants and animals. While the targeted transfer of recombinant DNA into crop plants remains a valuable tool to achieve a desirable breeding outcome, integration of transgenes into the host genome has been random, which in part, leads to reduced acceptance of GMOs by the general population in some parts of the world. Likewise, methods of induced mutagenesis, such as TILLING, have the disadvantage that many mutations are induced per plant, which has to be removed again by expensive backcrossing. Advances in genome sequencing have provided more and more information on differences between susceptible and resistant varieties, which can now be directly targeted and modified using CRISPR/Cas9 technology. By selecting specific gRNAs occurrence of off-target modifications are comparatively low. ZFNs and TALENs- based approaches required re-engineering a new set of assembled polypeptides for every new target site for each experiment. The difficulty in cloning and protein engineering prevented these tools from being broadly adopted by the scientific community. Compared to these technologies, designing the CRISPR toolbox is much simpler and more flexible. CRISPR/Cas9 is versatile, less expensive and highly efficient. It has become the most widely used technology for genome editing in many organisms. Since its inception as a powerful genome-editing tool in late 2012, this breakthrough technology has completely changed how science is performed. The first few chapters in this book introduce the basic concept, design and implementation of CRISPR/Cas9 for different plant systems. They are followed by in-depth discussions on the legal and bio-safety issues accompanying commercialization and patenting of this emerging technology. Lastly, this book covers emerging areas of new tools and potential applications. We believe readers, novice and expert alike, will benefit from this all-in-one resource on genome editing for crop improvement. Chapter 17 is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.