For more than 100 years, National Geographic has published some of the most iconic photos ever taken - capturing explorations, scientific expeditions, wildlife and cultures around the world.
Over the years, it has put together an astonishing collection of 11 and a half million photos and original artwork.
Now, the National Geographic Society is putting 240 of those pieces - from the late 1800s to today - up for auction for the first time.
They're being sold at Christie's in New York in December, to commemorate National Geographic's 125th anniversary. They're expected to bring in about $3 million.
Works of art from the fields of geography, archaeology, wildlife and world cultures are also going up for sale.
Among the photos up for grabs are...
'Afghan Girl' - a haunting image taken by Steve McCurry in 1984 during the Soviet invasion of Afghanistan. It's expected to sell for up to $50,000.
McCurry also has made a special print for the sale. Part of the proceeds from it will go to the Afghan Girls' Fund.
A portrait of Admiral Robert Peary in Cape Sheridan, Canada during his 1908 expedition to the North Pole.
And the face of an aborigine Huli Tribesman in Papua New Guinea, shot in 1998.
As well, there are paintings and illustrations - which National Geographic was known for in its early days.
Newell Convers Wyeth's painting of two pirates, 'The Duel on the Beach', is expected to be one of the biggest sellers - anywhere from $800,000 to $1.2 million.
A 40-volume photo portfolio and book by Edward Curtis entitled 'The North American Indian', is expected to fetch between $700,000 to $900,000.
And there's this illustration entitled; 'A Blue Globe Hanging in Space - The Earth As Seen From The Moon', by Charles Bittinger.
The sale also contains some images that have never been published, including a selection from Herbert Ponting, who took some of the most enduring images of the Antarctic.
The works are being auctioned to celebrate the society's legacy and to promote its image and video archive.
Proceeds will go toward the promotion and preservation of the archive and "the nurturing of young photographers, artists and explorers... who are the future of the organization," said Maura Mulvihill, senior vice-president of National Geographic's image and video archives.
The auction takes place on December 6 at Christie's Rockefeller Center location in New York.
National Geographic is one the world's largest nonprofit scientific and educational institutions.
It sponsors and funds scientific research and exploration through its official journal, 'National Geographic Magazine', which reaches nearly 9 million people in 36 countries, in 27 languages.
The society reaches millions more people through its National Geographic Channel, books and other sources.