This comprehensive book covers the theoretical and practical aspects of citron trees and fruit. The citron (Citrus medica L.), one of the three primary species ancestral to most citrus types, is used for traditional medicine and is highly revered in the Jewish religion during the Tabernacles feast, referred to by the name 'Etrog'. This book’s three sections address biology (botany, genomics, Chinese and Mediterranean citrons, diseases, pests, and horticulture), tradition (Talmudic discourse, mysticism, medicine, literature, art, food, and beverages) and history (archaeology, trade, grafting controversies); these sections are 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-renowned specialists from Israel, Italy, France, the U.S.A., China and Australia. The book is written in an accessible scientific style aimed at a wide range of readers.