Genome editing technology is important because it can be used to improve plant traits. The earlier genome-engineering tools, zinc finger nucleases (ZFNs), and TAL effector nucleases (TALENs) are complicated to design and not flexible. The novel genome editor, CRISPR-Cas systems, has advantages over ZFNs and TALENs. The advantages are simple and easy to design precision in targeting and efficiency. Due to its precision and simplicity, the CRISPR-Cas technology has rapidly become the most popular genome-editing platform in life-science fields. CRISPR-Cas technology has been used widely for human gene therapy to treat diseases and for plant breeding programs for crop improvement. This book is of interest and useful to genome-editing professionals, plant breeders, horticulturists, field-level extension workers, nurserymen, planters, ecologists, and valuable source of reference to the relevant researchers.