Coffee is a widely consumed stimulant beverage prepared from roasted seeds, commonly called beans, of the coffee plant. Coffee was first consumed in the 9th century, when it was discovered in the highlands of Ethiopia. From there, it spread to Egypt and Yemen, and by the 15th century had reached Persia, Turkey, and northern Africa. From the Muslim world, coffee spread to Italy, then to the rest of Europe and the Americas. Today, coffee is one of the most popular beverages worldwide.Coffee berries, which contain the coffee bean, are produced by several species of small evergreen bush of the genus Coffea. The two most commonly grown species are Coffea canephora (also known as Coffea robusta) and Coffea arabica. These are cultivated in Latin America, southeast Asia, and Africa. Once ripe, coffee berries are picked, processed, and dried. The seeds are then roasted, undergoing several physical and chemical changes. They are roasted to various degrees, depending on the desired flavor. They are then ground and brewed to create coffee. Coffee can be prepared and presented by a variety of methods.Coffee has played an important role in many societies throughout modern history. In Africa and Yemen, it was used in religious ceremonies. As a result, the Ethiopian Church banned its consumption until the reign of Emperor Menelik II of Ethiopia. It was banned in Ottoman Turkey in the 17th century for political reasons, and was associated with rebellious political activities in Europe. Coffee is an important export commodity: in 2004, coffee was the top agricultural export for 12 countries; and in 2005, it was the world's seventh largest legal agricultural export by value. Some controversy is associated with coffee cultivation and its impact on the environment. Many studies have examined the relationship between coffee consumption and certain medical conditions; whether the effects of coffee are positive or negative is still disputed.