This comprehensive book covers all theoretical and practical aspects of Etrog Citron trees and fruit. The Citron (Citrus medica L. ) is one of the three forefathers of the Citrus tribe, used in traditional medicine and highly revered in Jewish religion during the Tabernacles feast.   Its 3 sections address the biological (botany, genomics, China citrons, diseases, pests, horticulture), traditional (Talmudic discourse, mysticism, medicine, literature, art, food, and beverages) and historic (archaeology, Mediterranean trade, grafting controversy, Israeli citrons) topics; supplemented by a glossary and pictorial album. The 22 chapters, some new and some translated and considerably expanded from the 2018 Hebrew edition, were written by world renown specialists from Israel, Italy, France, U. S. A. , China and Australia. The book is composed in a light scientific style, (not over crowded with foot notes and technical methodology), in order to turn it attractive to a wide range of intellectual audience.