Long before the world was digital and we realised that it was made of bytes and pixels, there was instant still photography.
Polaroids were the creation of an American engineer called Edwin Land, who is said to have invented the process after his daughter asked him why she couldn't see the holiday snapshots they took together as soon as they took them.
Plenty of fathers of course would like to make that kind of wish come true, but Land's daughter was lucky.
Her dad wasn't just an indulgent parent, he was an engineer and inventor of genius - a 20th-Century Edison.
Land was said to wrap himself so intently in his work that his staff erected a barrier outside the front door of his office to prevent him from walking straight out into the traffic.
The world still lives with his inventions - polarising lenses that eliminate glare and the high-flying cameras in U2 planes and satellites that gave the United States the edge in the Cold War.
His first instant camera had to be manufactured with extraordinary precision so that a system of tiny rollers squeezed the developing chemicals out of the thick padded film at just the right rate.
The science and the manufacturing processes were complex, but the vision behind them was simple: Land wanted to give families photographs that developed in their hands.
He had an artistic vision too, based on giant studio cameras he designed - behemoths the size of bedroom closets that produced large format (20 x 24 inch) prints.
Land gave photographers free access to these cameras and in return kept some of the prints they produced.
The result was the Polaroid Collection, which is being sold by auction at Sotheby's in New York this week.
David Levinthal is one of the artists in the collection. His quirky, compelling pictures catch the eye.
He tells American stories through elaborately-staged pictures of toy figurines which trick the viewer's sense of scale and challenge our sense of what is real.
His most immediately recognisable slices of Americana are his iconic shots of cowboys, but there are darker and more challenging aspects to his work too.
He has made studies of America's modern wars using model soldiers. His famous shots of scantily clad dancers have a disturbingly erotic aspect to them.
Levinthal jokingly compares being given access to Polaroid's extraordinary studio camera with being given a sample of crack by a drug dealer.
"I was hooked," he told me.
"One of the wonderful things about the camera is that you completely lose any sense of scale. It could be life-sized, it could be eighteen inches."
The ordinary Polaroid camera did something equally remarkable for families all over the world.
Until it came along in 1948, photography was a tiresome business.
Unless you had your own darkroom, rolls of film had to be sent away to developers or left at pharmacies, then collected days or even weeks later.
Land's invention transformed an industrial process into something that happened in your hand.
The sheets of shiny card on which the instant photographs materialised were each in their own way tiny laboratories where 35 different components and chemicals combined to produce a minor miracle.
Consumers loved them and they sold in millions all over the world - bringing competitors like Fuji into the market too.
On the face of it, that should be that. The Polaroid camera ought to be remembered as a powerful tool for photographic artists and an iconic consumer product of the past - as outdated as the hand-mangle or the hula hoop.
In theory, digital photography has superseded the Polaroid camera as comprehensively as the CD eclipsed the wax cylinder.
Except that Polaroid photography just refuses to die.
Uncertain and imperfect
Florian Kaps runs a business selling recovered and reconditioned Polaroid cameras. He even manufactures new film stock for them.
He is not in other ways a Luddite. As far as I know he doesn't have a valve radio or a black and white TV; he does use an iPhone and a laptop.
But he sees in Polaroid photography an almost mystical point where science and art overlap. His customers are people who find the digital age just a little too digital.
The Polaroid process has a hint of uncertainty about it - the temperature at which the film develops can change the appearance of the finished shot for example.
And unlike digital pictures which can endlessly be reproduced, every Polaroid is unique and unrepeatable.
Or, as Mr Kaps more artistically puts it: "Sometimes the imperfections and the uncertainties can be fascinating."
Mr Kaps points out that Polaroid, in its heyday, was a fascinating commercial company whose new product launches created the same kind of buzz which you would associate with a business like Apple in the modern world.
Living, breathing medium
Mr Kaps's thoughts on the artistic imperfection and uniqueness of every Polaroid photograph strike a chord with Grant Worth, a young American artist who works in Polaroid.
He, too, sees the playfulness of a type of film which reacts to different lights and temperatures like a living, breathing medium.
He loves the integrity of Polaroid. In a world where digital processing can paint us into pictures of meetings we never attended or airbrush us out of the snapshots of friends we fall out with, Grant has gravitated towards the authenticity of the old Polaroid process.
"In 2010," he explains, "we have to question every image we see. Does that woman really have that body? Is that building really there? For my work it's important to me to know that what took place really took place."
That point is a reminder of another difference between digital technology and the old world it replaced. You can like digital cameras, appreciate their convenience and use them every day.
But they will never be something to love in the way that Polaroids became - and 50 years from now when they too have been superseded it is hard to see anyone sitting down to write this kind of romantic re-appraisal of their worth.