Sherpa Tenzing Norgay had tried to climb Mount Everest, the highest mountain in the world, six times before his successful climb with Edmund Hillary in 1953. His son, Jamling Norgay, spoke to Louise Clarke about the spiritual importance of the mountain for his father, and how Tenzing Norgay saved Hillary’s life when he fell down a crevasse on the mountain. (Photo: Tenzing Norgay and Edmund Hillary. Credit: BBC)

On 29 May 1953 Edmund Hillary, climbing with sherpa Tenzing Norgay, became the first people to reach the summit of Everest. The two men instantly became famous all over the world. Edmund Hillary’s son, Peter Hillary, tells Louise Clarke about his father's heroic climb. (Photo: Tenzing Norgay and Edmund Hillary. Credit: BBC)

On 31 May 1970, the Huascarán avalanche, caused by the Ancash earthquake, destroyed the town of Yungay, in Peru. Only 400 people, out of a population of 18,000, survived. A clown, named Cucharita, saved approximately 300 children, who were at a circus performance, by leading them to higher ground. Rachel Naylor speaks to his son, Christian Peña. (Photo: Statue of Christ at the cemetery overlooking Yungay, after the avalanche. Credit: Science Photo Library)

On 25 May 1963, leaders of 32 newly-independent African nations came together for the first time in the Ethiopian capital Addis Ababa. At stake was the dream of a united Africa. In 2013, Alex Last spoke to Dr Bereket Habte Selassie who took part in that first gathering. (Photo: Haile Selassie, centre, and Ghana's first President Kwame Nkrumah, left, during the formation of the Organisation of African Unity. Credit: STR/AFP via Getty Images)

On 31 May 2013, a huge tornado hit an area close to El Reno in the US state of Oklahoma. It was the widest tornado ever recorded and produced extreme winds of more than 400 kilometres an hour. Eight people were killed, including three storm chasers. One of the people tracking the storm was Emily Sutton, a meteorologist with KFOR-TV in Oklahoma City. She’s a member of the station’s storm chasing team and was caught in the tornado. She tells Rob Walker about the impact that day had on her and other storm chasers. (Photo: Cars damaged by the El Reno tornado. Credit: Joe Raedle via Getty Images)