The novel is set in A.F. 632, approximately seven centuries after the twentieth century. A.F. stands for the year of Ford, named for the great industrialist Henry Ford who refined mass production techniques for automobiles. World Controllers rule the world and ensure the stability of society through the creation of a five-tiered caste system. Alphas and Betas are at the top of the system and act as the scientists, politicians, and other top minds, while Gammas, Deltas, and Epsilons are at the bottom and represent the world's industrial working class. A drug called soma ensures that no one ever feels pain or remains unhappy, and members of every caste receive rations of the drug. Pre- and post-natal conditioning further ensures social stability. Brave New World opens with the Director of the Central London Hatchery and Conditioning Centre giving a group of young students a tour of the facilities. An assembly line creates embryos using the latest advancements in science. The students view the various techniques for producing more babies and watch as the process segregates babies into various castes. After the babies are decanted from their bottles, they are conditioned through Neo-Pavlovian conditioning and hypnopaedia. In Neo-Pavlovian conditioning, babies enter a room filled with books and roses. When the babies approach the books or the roses, alarms and sirens sound, and the babies receive a small electric shock, which frightens them so that when they confront the same items for a second time, they recoil in fear. Hypnopaedia teaches babies and children while they are asleep by playing ethical phrases numerous times so that the phrases will become a subconscious part of each person.