The lay practice of adoration formally began in Avignon, France on September 11, 1226. To celebrate and give thanks for the victory over the Albigensians, King Louis VII of France asked the Bishop of Avignon to have the Blessed Sacrament exposed in the Chapel of the Holy Cross. The throng of adorers was so great that the bishop decided to have the adoration continue day and night. During the Middle Ages, many more of the faithful began to adore the Blessed Sacrament apart from the Mass. At first, the custom was to worship the host reserved in the tabernacle. Eventually, some came to practice the devotion with the tabernacle doors open. Later still, solemn exposition of the host, in a monstrance, became the norm. The practice spread through Europe and culminated in the establishment of the Feast of Corpus Christi—Latin for “the Body of Christ”—in 1264. The feast itself, now celebrated each June, helped spread the devotion. It was not until after the Council of Trent, however, that perpetual adoration began to develop on a worldwide scale. During the Protestant Reformation, church lootings were common, as were desecrations of the Blessed Sacrament. Faithful Catholics made reparation to God by keeping a loving vigil before Him, around the clock. Perpetual adoration became a symbol of constancy in a volatile age. Throughout Europe and eventually America, new religious orders arose centered on uninterrupted Eucharistic adoration. In 1907, the Catholic Encyclopedia could state that such orders were too numerous to list. In the years following the Second Vatican Council, the devotion began to wane, only to rise again in popularity with the encouragement of Pope John Paul II. At 128 years and counting, the Franciscan Sisters of Perpetual Adoration have the oldest Adoration program in the United States. - This is taken from the St. Maximilian Kolbe Shrine Website.