Although the science of genetics is relatively new, people have understood the hereditary nature of traits and have "practiced" genetics for thousands of years. The importance of genetic and environmental factors in orthodontics has been discussed mainly with reference to the etiology of malocclusions. Little thought has been given to the effect of genetic and non-genetic factors on orthodontic therapy and the stability of treatment results. The same holds true for the changes in facial appearance and dental conditions taking place between adolescence and old age. Until adulthood, the permanent interaction between genetic and environmental factors guides and controls the process of growth and development and determines the morphologic and physiologic traits of the individual. There is adequate evidence that many developmental conditions are primarily under genetic control. This book will give a brief review of the history of genes in various malocclusions.