ROME - Inside a chapel on the edge of Rome, a nun uses a key to open a wooden wall panel, revealing a hidden niche. Behind glass and stitched loosely to supporting backing hangs a relic of holy suffering: the bullet-pocked, bloodstained undershirt that John Paul II was wearing when a gunman shot him in the stomach in St. Peter's Square.
The short-sleeved garment bears the initials "JP," sewn in red cotton thread on the label by nuns who did his laundry. Jagged rips run down from the neck and sides, made when emergency room staff tore open John Paul's shirt as they raced to save the 60-year-old pontiff's life.
It's one of the most remarkable of the endlessly surfacing relics of John Paul, who will be declared a saint on Sunday in the very same square where a Turkish would-be assassin shot him on May 13, 1981.
Relics of John Paul have enjoyed a boom ever since the beloved pope was beatified in 2011, and they are gaining heightened significance -- as well as a surge of veneration -- ahead of his canonization. The phenomenon has been fueled by John Paul's longtime Polish confidant and secretary, Stanislaw Dziwisz, who doles them out to churches that request them. The Vatican also played a role in the relic fever by breaking its own rules to allow worldwide veneration of John Paul's relics as soon as he was beatified, rather than waiting until he became a saint.
The famous undergarment was discovered by the head nurse in the operating room at Rome's Gemelli Polyclinic as she was cleaning the floor.
"She understood that the undershirt could be important," said Sister Amelia Cicconofri, who displays the undershirt at Regina Mundi church upon request. "She picked it up, rolled it in a towel and kept it in her closet at home."
Nurse Anna Stanghellini, who lived out her last years at the church's convent, donated the shirt to the nuns there, bequeathing a vivid and tangible testimony to John Paul's physical suffering.
Relics of John Paul are by no means limited to Rome. John Paul was the world's first globe-trotting pope, and he left things associated with him scattered around the globe. To qualify as a relic, an object needs only to have been in physical contact with the saint in question.
The Manila area restaurant where John Paul dined during his 1995 pilgrimage to the Philippines shows off the spoon, fork, water goblet, knives and table napkin -- all still unwashed after his meal of grilled fish and fried shrimp. Elsewhere in the predominantly Catholic Asian nation, shopping malls this month are showing strands of his silvery-white hair and a piece of bedsheet from his deathbed.
Irish Julia Feniquito, a 24-year-old nurse in the Phiippines' Quezon City, was still wearing her blue scrubs and looking to buy a dress when she passed by a traveling exhibit of John Paul relics in one shopping mall. She kneeled to pray for several minutes in front of a makeshift altar and wrote her reflections on a sheet of paper, which she slipped into a box under a papal skull cap.
"His aura, when you first see him, you can tell that he is very holy," Feniquito said.
"John Paul II probably has stuff all over the place," considering he was the third-longest serving pontiff, said the Rev. Raymond Kupke, a professor of church history at Seton Hall University in New Jersey. "If you think of all the places he has been, the amount of relics is enormous."
A tiny church in the Naples hinterland packed its pews for nine days earlier this year when it displayed a gold-covered reliquary containing a drop of papal blood drawn for analysis from John Paul on his last day on Earth. For the faithful, it's a profoundly moving testament to the pope's courage in the face of death and suffering.
"This was the last blood taken from the Holy Father, his last day of life," said the Rev. Jonas Gianneo, pastor of Santa Maria Francesca delle Cinque Piaghe church in Casoria. The pastor said that the drop came from a vial of blood saved by Dziwisz, now cardinal of Krakow.
Amid the proliferation of John Paul relics, Vatican experts say, it's important to make key distinctions: Relics are categorized by the Vatican as "first-class" (those that are part of the saint's body, such as bones or blood), "second-class" (items owned or used by a saint) and "third-class" (mostly things that were touched by the saint).
It's not just rank-and-file faithful who cherish a relic of John Paul.
Monsignor Piero Marini, John Paul's right-hand man for decades, told The Associated Press that "every now and then" he kept some of the handkerchiefs the pontiff used in ceremonies, especially the last ones.
"I still have them," Marini said.
He also kept some cloth stained by blood when John Paul once caught a pinky in a car door. That's a decidedly minor event compared to a papal assassination attempt - and Marini expressed awe of the bloodied undershirt.
"When they put it under glass," he said, "I had a vision of almost an icon of the undershirt, because you saw the wounds, the blood."
True relics "are those of the body," Marini said. "The body is the place where the Holy Spirit produced its effect, where it worked."
Selling relics is sacrilegious -- but nothing stops the faithful from making a "donation" to whoever provided the relic, or purchasing the often ornate container holding the relic itself.
Relics are particularly prized in John Paul's native Poland - and there, too, Dziwisz' influence is everywhere felt.
In Krakow, there is a vial of John Paul's blood drawn in 2005 before a tracheotomy. In the pope's birth-town, Wadowice, a reliquary in the basilica holds a drop of his blood. His first home is also a popular attraction.
"Something tangible must be left behind. A proof that he really existed," said Bogusia Weglik, a middle-aged woman from Wadowice, after praying at the basilica. "Something for the next generations, or else they will turn wild."
The other pope to become a saint on Sunday - John XXIII - has not attracted anywhere near the relic frenzy of John Paul. John XXIII, who called the revolutionary Vatican II Council, only served as pope for 4½ years, and there are simply not that many objects associated with him.
"Fifty years (after his death) there aren't relics, not only first-class ones, but not even second-class ones," said Monsignor Giulio Dellavite, an official of the diocese of Bergamo, in northern Italy, where John XXIII grew up. "We receive requests from all over the world, for relics for altars, but we cannot satisfy them."
However, an urn containing bone fragments from John XXIII used in his Vatican saint-making ceremony will be sent to Bergamo's cathedral, so the faithful will be able to venerate him there.
At Rome's Regina Mundi church, pilgrims - mainly from Poland - come in tour buses to pray before John Paul's undershirt. Occasionally solitary visitors wanting to see it also ring the convent bell. Recent entries in the guest book were written in Italian, Portuguese and Spanish.
"Dear St. Pope," wrote one person - well before the Vatican's official decision on John Paul's canonization.