In 2009, the Indian government embarked on an ambitious task to register all of the country's billion-plus citizens with a unique digital ID. Aadhaar - which means foundation in many Indian languages - became the world's largest ever biometrics project. It allowed millions of people to open bank accounts or access a mobile connection for the very first time. But the project also attracted considerable opposition from privacy advocates and civil rights groups, who brought a case that went all the way to India's Supreme Court. Dan Hardoon speaks to Nandan Nilekani, who chaired the Aadhaar projec ..read more

In 1963, Dr Jose Ignacio Barraquer Moner performed the first surgery on a human eye aimed at correcting short-sightedness. The ophthalmologist had been developing his technique for years, believing that there was a better solution for blurry vision than wearing glasses. But he had to move from Spain to Colombia to begin his experimental surgery which involved dry ice, a watchmaker’s lathe and rabbits. The idea was to change the shape of the cornea – the front layer of the eye - to focus vision. First, he sliced off the patient’s cornea then dunked it in liquid nitrogen, before using a miniatur ..read more

In the 1980s, a thirst for caffeine caused an unusual global collaboration. Coffee-loving East Germans were left without after a crop failure in the world’s biggest exporter of the drink, Brazil. So the East Germans hatched a scheme, linking up with fellow communist state Vietnam to create a mass of coffee plantations. The man behind the plan, Siegfried Kaulfuß, tells Michael Rossi about the scale and success of the endeavour. (Photo: Siegfried Kaulfuß with Vietnamese coffee farmers. Credit: Siegfried Kaulfu ..read more

When a new show called Friends hit American TV screens in September 1994, it made household names of its cast. Over 10 series, it charted the lives of six young New Yorkers, through marriages, divorces, births and deaths. The final episode was broadcast on 6 May 2004. In 2014, executive producer Kevin Bright told Farhana Haider how the show was born - and how it became one of the biggest comedies of all time. (Photo: The cast on the last day of filming. Credit: David Hume Kennerly/Getty Images ..read more

Thirty years on from the opening of the Channel Tunnel between Britain and France, we look at the moment the two halves of the tunnel were connected in 1990. Graham Fagg was the man who made the breakthrough, and the first person to cross by land between the two countries in 8,000 years. In 2010, he told Lucy Williamson about the festivities of that day. (Photo: The moment of breakthrough Graham Fagg greets Frenchman Philippe Cozette. Credit: AFP/Getty Images ..read more

In February 2014, Ukraine’s ousted president, Viktor Yanukovych fled the country. His estate was abandoned by security guards, so for the first time ordinary people got to see inside Mezhyhirya, the extraordinarily extravagant home of the former president. Denys Tarakhkotelyk was one of those early visitors, and went on to take charge of the estate. He tells Gill Kearsley his remarkable story, and how the house became known as a ‘museum of corruption’. (Photo: People wander around President Viktor Yanukovych's Mezhyhirya estate. Credit: Jeff J Mitchell/Getty Images ..read more

In 1936, Dale Carnegie wrote one of the world’s most popular self help books - How to Win Friends and Influence People. The idea was suggested by a book editor who had attended one of Dale’s public speaking courses in New York. The result was a mix of psychology, philosophy and good old-fashioned common sense. Dale offered advice like: Smile. Give praise. Be a good listener. And remember people’s names. The book went on to become a best seller. Today, more than 30 million copies have been sold worldwide, and it has been translated into 36 languages. Even the title is part of popular culture. D ..read more

In 1961, the American psychologist Stanley Milgram began a series of controversial experiments on ‘obedience to authority’. His study aimed to show how ordinary people could be capable of committing evil acts, if ordered to do so. He wanted to understand the psychology behind genocide, telling the BBC: “How is it possible that ordinary people who were courteous and decent in everyday life, can act callously, inhumanely, without any limitations of conscience?” During the tests, participants were led to believe that they were assisting an unrelated experiment, in which they had to administer ele ..read more

On 13 December 1990, the anti-apartheid politician Oliver Tambo returned to South Africa after 30 years in exile. As the president of the banned African National Congress (ANC), he had lived in Zambia building the liberation movement while other key ANC members including Nelson Mandela and Walter Sisulu were political prisoners. By lobbying around the world and attracting talented South African exiles such as Thabo Mbeki, he built the organisation into a legitimate contender for government. When President FW de Klerk unbanned the ANC, Oliver or OR Tambo was finally able to return home where he ..read more

In August 2002, the remains of an indigenous South African woman called Sarah Baartman were returned to South Africa after almost 200 years away. Sarah died in Paris in 1815 after being forced to perform in European 'freak shows' where people considered to be biological rarities were paraded for entertainment. She had been subjected to racist and degrading treatment and her remains were exhibited at a French museum until 1976. When Nelson Mandela became the president of South Africa in 1994, he requested that Sarah's remains be returned to her homeland. However, by 1998 that had not happened ..read more