Jeff Widener holds his photo of Tank Man in Tienanmen Square from 1989. Photo: Tim Mantoani

Steve McCurry holds his 1984 photo of a young woman from Peshawar, Pakistan. "I looked for this girl for 17 years and finally found her in 2002. Her name is Sharbat Gula." Photo: Tim Mantoani

Neil Leifer holds his photo, Ali vs. Liston*, which he took on May 25, 1965 in Lewiston, Maine.* Photo: Tim Mantoani

Bill Eppridge stands with his photo of Robert F. Kennedy after his assassination on June 5, 1968. Photo: Tim Mantoani

Elliot Erwitt: "The picture I am holding was snapped in 1974 just across the street from my apartment in New York's Central Park. It has been 38 years since that event and sadly I have lost track of the participants." Photo: Tim Mantoani

Brent Stirton: "This is Virunga, the first National Park in Africa, in the Democratic Republic of Congo. The Silverback Mountain Gorilla, along with 6 females, had been killed by a group trying to intimidate conservation rangers into being less proactive in their efforts against poaching & illegal charcoal making. There are only about 40 of these Silverbacks in the world, so the Rangers were devastated at the assassination. This procession went on for about 5 kms, moving the 600 pound body over hills & through the forest. Over 120 of these rangers have died in the last 10 years doing this job; most make less than $10 a month. They're heroes, there's just no other word that seems appropriate to describe these incredible African men." Photo: Tim Mantoani

Brian Smith: "The magic of photography happens when you don't see what's coming next." Photo: Tim Mantoani

Douglas Kirkland: "This is from my Evening with Marilyn." Photo: Tim Mantoani

Harry Benson: "Brian Epstein — Beatles' manager — had just told them they were number one in America, and I was coming with them to New York, 1964." Photo: Tim Mantoani

Karen Kuehn: "From the 1993 Cats Story shot for National Geographic. The director Thomas Kennedy asked me to shoot an entire story about 'cats.' He did not want it to be typical! So problem solving this assignment was good fun. The Russian Blue Cat and Ballerina legs was inspired by George Balanchine — he used the idea of cats landing always on their toes to teach his dancers." Photo: Tim Mantoani

Lyle Owerko: "No one knew such a beautiful warm day would serve as the backdrop to one of the most painful and confusing events to the heart of mankind. This picture is one small part of such a huge event that ties the threads of thousands of stories and millions of people together. Written words will never convey the whole scope of the event, nor even summarize the sounds, the smells or even the voices that are frozen in my memory bank from that day. I did the best job I could in photographing 9/11 so that future generations would have an idea of the scope of what happened, to have the evidence of how innocence can so easily be snatched away in a razor's edged moment of time. My hope is that in time the wounds and pain will heal and that wisdom and peace will prevail among the darkness of this event, so that humanity can move forward into a time of grace and understanding." Photo: Tim Mantoani

Mark Seliger: "Originally an inside opener for Rolling Stone cover story of Nirvana in conjunction with the release of In Utero*, my first Polaroid (with Negative) was by far the most emotional and revealing of his spirit. Two months later Kurt died from a self-inflicted gunshot wound to his head. This photograph became the memorial RS cover."* Photo: Tim Mantoani

Mary Ellen Mark: "I am holding my photograph of Ram Prakash Singh and his beloved elephant Shyama — taken in 1990. Ram Prakash Singh was the ringmaster of "The Great Golden Circus." The photograph was done in Ahmedabad India. This was part of my Indian Circus Project. I love India and I love the circus so photographing eighteen circuses all around India was an incredible experience. Unfortunately, Shyama died a few months after this photograph was taken. Supposedly he succumbed to a poisoned chapatti. Ram Prakash Singh was heartbroken. Me also." Photo: Tim Mantoani