Zimbabwe's President Robert Mugabe (left) greets South African President Nelson Mandela in Harare, Zimbabwe, in 1998. The two men have shaped their countries in dramatically different ways. Rob Cooper/AP hide caption

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A well-wisher uses his phone to take a picture of a banner of photos of Nelson Mandela outside the Mediclinic Heart Hospital in Pretoria, where the former South African president is being treated. Ben Curtis/AP hide caption

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Schoolchildren sing 'Happy Birthday' to former South African President Nelson Mandela at Phefeni High School, opposite Mandela's former home in Soweto Township on Thursday in Johannesburg, South Africa. Christopher Furlong/Getty Images hide caption

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On the eve of Nelson Mandela's 95th birthday, street vendors in Pretoria, South Africa, were selling T-shirts to mark the occasion. Madiba is Mandela's tribal name. Christopher Furlong/Getty Images hide caption

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In 1990, Nelson Mandela (wearing a dark suit, pointing down) visited the graves of family members in Qunu, South Africa. A grandson's 2011 decision to move some relatives' remains to another site was followed by a lawsuit and court action. Juda Ngenya /Reuters /Landov hide caption

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Near the end of his 27 years in prison, Nelson Mandela was taken to secret meetings with government officials and for drives around Cape Town. Here, he returned to his Robben Island prison cell for a visit in 1994, shortly before he became South Africa's first black president. Louise Gubb/Corbis hide caption

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A family brings a message of good wishes for former South African President Nelson Mandela outside his house in Johannesburg Monday. Mandela, 94, is in critical but stable condition. Stephane De Sakutin/AFP/Getty Images hide caption

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President Obama looks out the window of the Robben Island prison cell that once held Nelson Mandela. The president and his family visited the prison on Sunday. Gary Cameron /Reuters /Landov hide caption

itoggle caption Gary Cameron /Reuters /Landov

Friday in Pretoria, South Africa, people gathered outside a hospital to pray for former President Nelson Mandela. He remains in critical condition with a lung infection. Jeff J. Mitchell/Getty Images hide caption

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Children release 95 balloons to mark Nelson Mandela's upcoming birthday outside the Mediclinic Heart Hospital where Mandela is being treated for a recurring lung infection in Pretoria, South Africa. Chip Somodevilla/Getty Images hide caption

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