Riccardo Levi-Setti, an Italian-born Holocaust survivor who became a pathbreaking physicist at the University of Chicago, uncovering subatomic particles while traveling the world in search of trilobites, ancient arthropods he called “the butterflies of the seas,” died on Nov. 8 at a nursing home in Chicago. He was 91.

His son Emile Levi Setti said the precise cause was not immediately known.

Raised in an aristocratic Jewish family in Milan, Dr. Levi-Setti was a teenager during World War II, when he hid from the Nazis and their fascist collaborators in a remote farmhouse, a slew of mountain caves and an empty underground fuel container near Genoa.

While on the run, he also developed a lifelong interest in fossils – possibly the result of scrambling across a fossil-filled rock pile while evading German patrols, his son said – and in physics, after studying with a friendly graduate student in the field.

Levi-Setti joined the University of Chicago in 1956 as a research associate, and over the next decade conducted experiments that set the stage for the discovery of strange quarks, one of the “fundamental building blocks of matter,” according to Chicago physicist Henry Frisch. His work centered on hyperons and mesons, a pair of subatomic particles, as well as cosmic rays, high-energy radiation that he studied using flights of balloons.

At the same time, Levi-Setti developed new techniques to track the paths of particles through space, sometimes using a superheated vessel known as a bubble chamber. “The images of the tracks of elementary particles, colliding with each other and perhaps creating new particles, have an astounding beauty of their own,” physicist Dietrich Müller, a professor emeritus at the University of Chicago, said in a statement.

“I think the aesthetic value of these images intrigued him just as much as the underlying physics,” he said, adding that Levi-Setti “belonged to the class of people to whom beauty and scientific discovery are exquisitely interwoven.”

In the early 1980s, Levi-Setti turned from particle physics to develop a scanning ion microprobe, an instrument that enabled him to take extraordinarily high-resolution images of teeth, DNA and almost anything else that struck researchers’ fancy.

Sometimes called the scanning ion microscope, it was not simply a viewing device, but could “see, taste and write,” Levi-Setti boasted, analyzing the chemical composition of objects, arranging individual atoms and even etching lines so tiny “that it could write 100 books, each containing 1,000 pages, on the head of a pin,” according to one account in the Chicago Tribune.

The instrument used a beam of gallium ions and was developed with Hughes Research Laboratories, a Malibu, California-based R&D lab created by billionaire Howard Hughes. It could bring objects as small as one-millionth of an inch into focus, Levi-Setti said, with a resolution that was about 100 times better than most electron microscopes on the market.

“It’s unbelievable what a kidney stone looks like under our machine,” he told the Tribune. “You can see the layers, like the sediment at the bottom of a lake, that were laid down meal after meal.” He also used the instrument to examine fibers in the Shroud of Turin, the purported burial shroud of Jesus, uncovering traces of limestone that may have come from Jerusalem – grist for believers in the cloth’s authenticity.

Amid his work at the University of Chicago, where he led the Enrico Fermi Institute for experimental physics from 1992 to 1998, Levi-Setti traveled across the Czech Republic, Wales, Newfoundland and Morocco to collect thousands of trilobite fossils.

In an email, the paleontologist and noted trilobite researcher Richard Fortey wrote that Levi-Setti was “much more than the smitten amateur,” publishing an influential paper in Nature regarding the “crystal eyes” of trilobites; discovering two new trilobite species; and helping general audiences understand the extinct animal with his 1975 book “Trilobites,” which was republished in 1993.

“Trilobites tell me of ancient marine shores teeming with budding life, when silence was only broken by the wind, the breaking of the waves, or by the thunder of storms and volcanoes,” Levi-Setti wrote in the work’s preface. “No footprints were to be found on those shores, as life had not yet conquered land. Genocide had not been invented as yet, and the threat to life on Earth resided only with the comets and asteroids.”

He continued: “All fossils are, in a way, time capsules that can transport our imagination to unseen shores, lost in the sea of eons that preceded us. The time of trilobites is unimaginably far away, and yet, with relatively little effort, we can dig out these messengers of our past and hold them in our hand. And, if we learn the language, we can read their message.”

Riccardo Paolo Levi was born in Milan on July 11, 1927. His father was a furrier and decorated World War I veteran, and his mother was a homemaker. With anti-Semitism on the rise under fascist leader Benito Mussolini, the family converted to Catholicism in 1934, and later fled to Pieve del Cairo, near the northern city of Pavia.

Riccardo had just turned 16 when, in July 1943, the Mussolini regime fell. Two months later, after the new Italian government announced its surrender to the Allies, German forces swept into the northern half of the country. The family was on vacation in Fontanigorda, a mountain resort, when a friend arrived to tell them their apartment in Milan had been seized by the SS.

By chance, Riccardo’s mother was on her way to the home to pick up supplies, according to a reminiscence of the period written by Levi-Setti. She was saved from entering the apartment by a neighbor, who took her to a nearby convent where she hid under a pile of coal and was eventually rescued by Elisa Setti, Riccardo’s godmother.

She was soon joined by Riccardo’s father, who came down with dysentery while hiding with Riccardo in the mountains. Levi-Setti remained there alone until meeting up with fighters in the Italian Resistance, and said that by the time the Germans surrendered, in 1945, he, too, was sick with dysentery.

“Recovered after a few weeks, I began to study for admission to the University,” Levi-Setti wrote. “In three months, I was able to make up four lost years of high school. It took me years to be able to sit at a restaurant without a good view of the entrance door.” By his count, 11 of his relatives were killed by the Nazis.

With his older brother, Franco, who had been studying in England when the war broke out, he gave himself the hyphenated name Levi-Setti, in honor of the woman who helped their parents survive. (His children do not use a hyphen in their last name.)

He graduated from the University of Pavia in 1949 and, according to his family, came to the U.S. on a Fulbright scholarship seven years later, traveling by boat. He had originally purchased a ticket for the Andrea Doria, an ocean liner that collided with another vessel and killed around 50 passengers off the coast of Nantucket, before his father insisted he take an earlier voyage on a different ship.

Levi-Setti was named a full professor of physics at the University of Chicago in 1965 and retired as an emeritus professor in 1999. In 2014 he published “The Trilobite Book,” a full-color follow-up to his original guidebook.

His first marriage, to Katharine McCarthy, ended in divorce. Survivors include his wife of 41 years, Nika Semkoff Levi-Setti of Chicago, a former teacher and public relations manager at the Field Museum; two children from his first marriage, Emile Levi Setti of Santa Monica, California, and Matteo Levi Setti of San Diego; and two granddaughters.

In a 2003 interview with the University of Chicago Magazine, Levi-Setti said that he found working with trilobites “relaxing.” It was, he said, a reprieve from writing academic papers and thinking about physics – while at the same time, offering a bit of perspective in geologic time. “It’s nice,” he said, “to think of life when man was not around.”