It was a photograph of three naked young boys running into the surf of Lake Tanganyika that brought home the potential of this new medium to Henri Cartier-Bresson.
"I suddenly understood that photography can fix eternity in a moment," said the father of modern photojournalism.
The roots of photography in the early 19th century involved clunky equipment and toxic chemical processes, which meant it was confined to the studio.
Then, in the 1930s, a new camera was developed that would change the way we see our world forever. The Leica compact was small enough to carry around, allowing photographers such as Cartier-Bresson to move through a crowd unobtrusively. He could now capture the spontaneity for which he became renowned. (Apparently he painted all the shiny parts of his camera black to make his presence even more unobtrusive. )
It had become easier to document the seismic events of the 20th century, but at the start this was almost entirely in black and white.
Now, a new book attempts to restore brilliance to the iconic images that are our window into the past. The Colour of Time: A new history of the world, 1850-1960 features famous photographs coloured by Brazilian artist Marina Amaral.
Together with historian Dan Jones, Amaral sifted through 10,000 pictures before whittling it down to the 200 shown in the book.
Amaral says the colourisation process is similar to that of a traditional painting, but extensive research is key.
Before starting she finds as many references for the picture as possible. These would include details such as the colours of uniforms and the hues of clothing common at the time.
Cartier-Bresson dismissed colour photography as inferior to that of black and white, but Amaral believes colour makes it easier to create a personal connection with the past.
She told blogger Frederick Wertz of findmypast.com: "When I colourise a picture, I feel like I'm recreating an event that could have happened yesterday.
"Black and white photos are wonderful and powerful, but they can create an obstacle for this connection to happen in a more intimate and deep level."
THE LAST EMPRESS
This photograph of Chinese Empress Dowager Cixi was taken in 1908 by a diplomat's son, an amateur photographer, five years before her death,
We owe our insight into the final days of the Qing dynasty to a minor British baronet, Sir Edmund Trelawny Backhouse, who wrote his memoirs, Décadence Mandchoue, almost 60 years ago.
Empress Cixi was known as the "dragon lady" and "old master Buddha". She enjoyed dressing up and loved to be photographed. Her silk clothing was embroidered with pearls, and she wore jewels, jade and gold hairpins threaded through her hair.
She liked eating at midnight, the hour of the rat. She would be served 120 different dishes for each meal but would eat only two or three bites of some of the dishes because of her fear that she would be poisoned.
Backhouse's memoirs, written more than 30 years after the events they describe, include the salacious details of his seduction at the hands of the dragon lady. She had sent orders that she wanted to seduce him and who could disobey an imperial command?
According to his memoirs, Backhouse was advised by a eunuch that the "old ancestress will require the most contact: you must perfume whole person for the occasion. She has never seen a naked European of decent birth and will want to inspect you closely behind and before."
Backhouse wrote that the empress had "breasts which were those of a young married woman; her skin was exquisitely scented . her whole body, small and shapely, was redolent with la joie de vivre; her shapely buttocks, pearly and large, were presented to my admiring contemplation; I felt for her a real libidinous passion such as no woman has ever inspired in my pervert homosexual mind before nor since".
Cixi had risen from the position of imperial concubine and had effectively ruled the empire for 47 years from "behind the curtain", since women were not allowed to appear at meetings of male officials.
Some say she was murdered by her nephew, others that she was poisoned. Her death marked the end of the 350-year Qing dynasty.
FLAPPERS
They swore, smoked, drank, chopped off their hair and burnt their corsets. Flappers were young women challenging their parents' conventions in the Roaring Twenties. They turned ideas of how women were supposed to dress, act and think on their heads.
During World War 1 women entered the workforce and, after the war, in the 1920s, were not inclined to give up their independence.
As hemlines rose, authorities responded by imposing dress rules. Female bank employees, for example, couldn't wear sleeves shortened above the elbow, and hems couldn't be higher than 30cm from the ground. They could wear only dresses, and then only in black, blue or brown.
Officialdom's tape measure ruled the beaches as bathing costumes became more revealing.
Necklines could not be lower than armpit level and hems no more than 10cm above the knees. In this photo taken on a beach on the Potomac River in Washington DC, a park superintendent ensures women's bathing suits comply with regulations.
MIGRANT MOTHER
This photograph of a mother and two of her children became emblematic of the suffering that the Great Depression of the 1930s inflicted on ordinary Americans.
Photographer Dorothea Lange was driving through California in 1936 when she came upon Florence Owens and her five children in a pea-pickers camp. Owens had journeyed all the way from the Oklahoma dust bowl with her children but the crops had failed and the migrant workers were close to starvation.
"I saw and approached the hungry and desperate mother, as if drawn by a magnet. I do not remember how I explained my presence or my camera to her, but I do remember she asked me no questions. I did not ask her name or her history. She told me her age, that she was 32. She said that they had been living on frozen vegetables from the surrounding fields, and birds that the children killed. She had just sold the tyres from her car to buy food. There she sat in that lean-to tent with her children huddled around her, and seemed to know that my pictures might help her, and so she helped me. There was a sort of equality about it," Lange wrote.
Her subject's ravaged beauty touched a nerve with the public and the government was galvanised into action, but by then Owens and her children had moved on.
MATA HARI
Mata Hari is synonymous with the allure of the exotic femme fatale, although the truth was far more pedestrian.
She was born Margaretha Geertruida Zelle in 1876 in the Netherlands. Through various twists of fate she ended up as a dancer on the Paris stage.
She claimed to be an Indonesian princess trained in exotic rituals and Hindu dances. Men begged for her favours. One described how, apart from chiselled brass cupolas concealing her small breasts, she danced "bare, fastidiously bare from the nails of her fingers to her toes".
During World War 1 Mata Hari was accused of spying for the Germans. On February 13 1917, she was arrested by French authorities on charges of espionage. Her tendency to fabricate her past, which had ignited the dance stages of Paris, tripped her up during her interrogation and she was found guilty after a short deliberation.
On October 15 1917 the seductress who once had Paris on its knees was driven to Caserne de Vincennes, the barracks of the old fort in eastern Paris.
According to an eye-witness she refused a blindfold and, after blowing the firing squad a kiss, was executed.
ADOLF HITLER
This portrait was taken in the early 1920s when the little corporal was embarking on his road to dictatorship. Adolf Hitler had rapidly grown his support base in Bavaria and felt emboldened to try to seize power in Munich. In 1923 he and his Nazi followers staged what is now known as the Beer Hall Putsch, a comically amateurish operation.
After the botched coup Hitler was charged with treason. He was sentenced to five years in Landsberg prison but served only nine months.
Prison officials treated him like a distinguished guest. His wing was nicknamed "Feldherrnhügel" or "the general's hill". His confidant Ernst Hanfstaengl said visiting Hitler felt like walking into a delicatessen. "There was fruit and there were flowers, wine and other alcoholic beverages, ham, sausage, cake, boxes of chocolates and much more." (Hitler put on weight, but dismissed a suggestion that he exercise.)
A prison official wrote on September 18 1924 that the Nazi leader "was always reasonable, frugal, modest and polite to everyone, especially the officials at the facility". The prisoner didn't smoke or drink and "submitted willingly to all restrictions".
In Landsberg, Hitler dictated Mein Kampf to his fellow prisoners and fanatical disciples Emil Maurice and Rudolf Hess.
With his stodgy body, crazed glare and petulant pose, the overgrown schoolboy comes across as both ridiculous and menacing in this photograph. Who could imagine the malevolent buffoon would come to power 10 years later and drag the world into war in his pursuit of Aryan perfection? As it turns out, too few people.
BUCHENWALD
The thousand-yard stares and mangle of skeletal limbs in Buchenwald concentration camp brought home the scale of the Holocaust as no words could.
As the Allied forces liberated Europe from Nazi tyranny in 1945, the Buchenwald inmates had already taken over the death camp after most of the SS guards fled.
As well as being a death camp, Buchenwald was the site of experiments. One of them aimed at determining the precise fatal dose of a poison. According to the testimony of one doctor, four Soviet POWs were administered the poison, and when it proved not to be fatal they were "strangled in the crematorium" and subsequently "dissected". Two priests were crucified upside down.
A contemporary report in the Guardian described how Allied soldiers forced locals to witness the horror first-hand.
"A thousand of the citizens of Weimar marched six miles [9.5km] through lovely country to the Buchenwald concentration camp yesterday.
"There in groups of 100 they were conducted on a tour of the crematorium with the blackened frames of bodies still in the ovens and two piles of emaciated dead in the yard outside, through huts where living skeletons too ill or weak to rise lay packed in three-tier bunks .
"It was an experience they can never forget. Most of the women and some of the men were in tears as they moved from block to block. Many were crying bitterly. Some of the women fainted and could be taken no farther."
A clock in Buchenwald is permanently set at 3.15pm - the time the camp was liberated on April 11 1945 by the Sixth Armoured Division of the US army.
When the survivors came to be tallied there were 21,000 in all, including 4,000 Jews and 1,000 children.
NELSON MANDELA
This portrait of Nelson Mandela in traditional dress was taken by photographer Ellie Weinberg while Mandela was in hiding in 1961.
Mandela spent almost two months undercover in the tiny ground-floor flat of his friend Wolfie Kodesh in Yeoville, sleeping on a camp bed. For this photograph he wrapped himself in Kodesh's bedspread to suggest a kaross.
Mandela wore traditional dress when he was sentenced to five years' imprisonment in 1962 for leaving SA without permission and inciting workers to strike.
He said later: "I had chosen traditional dress to emphasise the symbolism that I was a black African walking into a white man's court."
As he returned to his cell at the start of the trial, a Colonel Jacobs ordered him to hand over his "blanket". Mandela refused to take off his kaross, telling the colonel he had no jurisdiction over his dress and he was prepared to take the matter all the way to the highest court. He was allowed to wear his kaross in court but not to and from court as, according to newspaper reports, it would "incite" other prisoners if they saw the traditional dress.
Kodesh described the atmosphere as Mandela entered the court: "It was incredible, because as he came up, there was a complete hush. Even the policemen . I honestly think they went pale to see this huge man standing there in his national costume. And that magistrate just looked, and he couldn't find his voice!"..