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 project.(Photo: Aadhaar system. Credit: Getty Images)

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 miniature lathe to carve the frozen cornea into the right shape. Next, he thawed the disc and sewed it back on. Jose’s initial surgery was performed on rabbits, but in 1963 he carried out the first procedure on a human patient, a 9 year old girl. It was a success, and soon doctors from around the world were flocking to Colombia to find out more.Barraquer called this procedure keratomileusis, from the Greek words for “carving” and “cornea.” The technique was the forerunner of Lasik eye surgery when the lathe was replaced with lasers.Jose’s daughter, Carmen Barraquer Coll followed her father into ophthalmology and tells Jane Wilkinson, how he inspired her.(Photo: Lasik eye surgery in 2009. Credit: BSIP/UIG Via Getty Images)

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 Kaulfuß)

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)

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)

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)

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.Dale’s daughter Donna Dale Carnegie tells Jane Wilkinson about the secret of its success.(Photo: How to Win Friends and Influence People in 1955. Credit: Frederic Hamilton/Hulton Archive/Getty Images)

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 electric shocks to another person.These fake shocks gradually increased to levels that would have been harmful had they been real volunteers.Vicky Farncombe looks back at the experiment, using BBC archive.This programme includes original recordings of the experiments which listeners may find disturbing.(Photo: Stanley Milgram beside the shock generator. Credit: BBC)

It’s 70 years since General Alfredo Stroessner seized power in Paraguay in a military coup. Stroessner remained in power for almost 35 years, before being toppled in 1989.More than 450 people were murdered under Stroessner's rule, with the fate of thousands more unknown. They are remembered as 'the disappeared' of Paraguay. One man has dedicated his life to finding the victims of Stroessner's dictatorship, including the remains of his own father. Rogelio Goiburu shares his story with Matt Pintus.(Photo: Rogelio Goiburu digging for the remains of Paraguay's 'disappeared'. Credit: Getty Images)

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 was greeted by a crowd of thousands at the airport.Oliver Tambo’s son, Dali Tambo, recalls to Josephine McDermott how his father and other ANC exiles danced in the aisle of the plane as they crossed into South African airspace.(Photo: Oliver Tambo at Jan Smuts Airport. Credit: AP/John Parkin)