This book is intended to provide an overview on variation among the tissues and plants derived from in vitro cell cultures and variants recovered from any form of cell cultures. Similarly, conventional plant breeding has traditionally been the sole avenue for crop improvement, however, recent demand of agriculture-based industry has shown that this process is too time consuming for typical corporate time frame. While variability has been obtained from wild species of cultivated crops, its access has been quite limited. The somaclonal and gametoclonal variations provides great promise for reducing the time required to produce new varieties or breeding lines which are easily patentable due to their novel variation. This book is useful for biologists, biotechnologist, geneticists and breeders, as well as a text book for undergraduates and graduate students specializing in plant biotechnology, genetics, genomics and plant breeding. Although the book has attempted to cover basic and applied information of somaclonal and gametoclonal variation in plants, many examples have been mentioned. It is hope that the book can also serve as a resource for related training courses.