Seminarians attend a theology class at the University of Saint Mary of the Lake at Mundelein Seminary in Mundelein, Ill. Courtesy of Mundelein Seminary hide caption

Face-to-face with Pope Francis: What do you say? Here, the pope arrives for his general audience at St. Peter's Square on Oct. 1, 2014, at the Vatican. He arrives in the U.S. on Tuesday. Vincenzo Pinto/AFP/Getty Images hide caption

Pope Francis' embracing of the digital world and social media has given new meaning to the word "followers" for the Catholic Church. Gabriel Bouys/AFP/Getty Images hide caption

Caryl Johnson (center) oversees communion at St. Mary Magdalene Community in Drexel Hill, Pa., as parishioners Janet Hamm and Jim Kalb assist. Unlike most traditional Roman Catholic services, a gluten-free bread and alcohol-free wine are offered. Jeff Brady/NPR hide caption

The church of Our Lady Queen of Angels in New York City's East Harlem neighborhood closed in 2007, but parishioners still congregate outside the parish for service every Sunday. Christopher Gregory for NPR hide caption

Pope Francis, in the Vatican's St. Peter's Square on Wednesday. The pope will begin his visit to the U.S. on Sept. 22 in Washington, D.C., where he will stay for several days before moving on to New York City. Giuseppe Ciccia/Barcroft Media/Landov hide caption

The altar where Pope Francis will celebrate Mass in Revolution Square in Havana near a government building decorated with the likeness of revolutionary hero Ernesto "Che" Guevara. The Mass is scheduled for Sept. 20. Desmond Boylan/AP hide caption

A stained-glass window depicting Father Junipero Serra in the Basilica Parish in Mission Dolores. Talia Herman for NPR hide caption

Vietnamese-Americans light candles at St. Helena, a Catholic church in Philadelphia, on April 4. Like many other once-struggling churches, St. Helena has been revitalized by immigrant parishioners. About 200 Vietnamese families worship at this church, along with others from Latin America, the Philippines and Africa. Matt Rourke/AP hide caption

Among bishops and priests, Pope Francis is in familiar — and lighthearted — territory. But among non-Catholics in the U.S., the pope's comments have also generated significant enthusiasm. Vincenzo Pinto/AFP/Getty Images hide caption

Carlos Alfaro, 19, practices with a soccer ball before a match in New York City. Some members of his youth soccer team are set to meet with Pope Francis in September. Hansi Lo Wang/NPR hide caption

Evan Fritz, head brewer at Manayunk Brewing Co., draws off some samples of Papal Pleasure, a beer concocted to mark Pope Francis' visit to Philadelphia. It's brewed with water blessed by a local priest. Emma Lee/WHYY hide caption