The colorful quilt of passports looks worn and faded.

They hang one above the other, remnants of a different time, gatekeepers in some cases for countries that no longer exist.

It took two doctoral students months to track down the expired documents found in Harvard University collections for their exhibit, “Passports: Lives in Transit.’’ It also includes many expired passports that the two students bought on eBay from strangers around the world, as well as visa applications and other items related to migration and travel.

The exhibit is on display at Harvard’s Houghton Library until Aug. 18.

Co-curator Lucas Mertehikian, who is studying romance languages and literature, said he and co-curator Rodrigo Del Rio wanted to explore the importance of these small booklets.

“Countries own passports, not people,’’ Del Rio said. “What happens with passports that belong to countries that don’t exist anymore, like the USSR or Yugoslavia?’’

Passports are telling, Mertehikian said, because they give insight into where people traveled, such as those who fled the Armenian genocide.

In one personal portion of the exhibit, Harvard student Anthony Otey Hernandez provided items that belonged to his late mother that told of her experience coming to the United States from Costa Rica.

“Passports always tell stories,’’ Mertehikian said, “much more than other kind of documents, which might be even more important in everyday life such as ID cards or driver’s licenses.’’

Among the passports borrowed from Harvard University for the exhibit are Russian revolutionary Leon Trotsky’s passport, a passport from Nazi-occupied Germany that belonged to prominent physician Gertrude Neumark Rothschild, and a passport for 19th-century American entrepreneur George Francis Train, who is said to have been the inspiration for the protagonist in Jules Verne’s “Around the World in Eighty Days.’’

“It’s easier for these passports to travel to the United States in their cancelled status than these people to travel to the United States,’’ Del Rio said of the passports they ordered online.

“It’s a very strange artifact because we own part of the history of these people in a way,’’ he said.

Cristela Guerra can be reached at cristela.guerra@globe.com. Follow her on Twitter @CristelaGuerra.