For seven centuries, Eucharistic adoration -- praying before an exposed consecrated Communion host -- was one of the most popular forms of devotion in the Roman Catholic Church, the focus of beloved prayers and hymns and a distinctive symbol of Catholic identity.

Following the modernizing reforms of the Second Vatican Council (1962-65), the practice fell from favor, especially in Europe and the U.S. But over the last decade, under Popes John Paul II and Benedict XVI, the church has strongly encouraged a revival of the practice.

"No one eat this flesh, if he has not adored it before; for we sin if we do not adore," Benedict said, quoting St. Augustine, in a 2009 speech at the Vatican.

Eucharistic adoration was also used as a teaching tool to reaffirm the doctrine of the "real presence" of Christ in the Eucharist, said the Rev. Richard P. McBrien, a noted theologian at the University of Notre Dame. For instance, McBrien said, devotion grew during the 16th- and 17th-century Counter-Reformation, in response to the arguments of some Protestant Reformers that the Eucharist was merely a symbol, not the actual body of Christ.

In 2005, according to Vatican statistics, there were about 2,500 chapels around the world -- including 1,100 in the U.S. -- that offered so-called "perpetual" round-the-clock adoration. Many other parishes now offer "holy hours," when the consecrated host is exposed for silent prayer or for services that include readings and hymns.

Adoration is also central to the Catholic Charismatic Renewal, one of the church's most dynamic and fast-growing movements, especially in the developing world.

Adoration appeals because it facilitates a "passive spiritual experience," said Adam Wilson, a spokesman for the Virginia-based Cardinal Newman Society. "It's a place where our Lord reaches out to the person, with the person having to do nothing but be present to our Lord," Wilson said.