Several babies born today have been deemed the symbolic 7 billionth person — including a little girl named Nargis in Lucknow, India. Here she is with her mother, Vinita.

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Watch as global population explodes from 300 million to 7 billion.

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Lujiazui, Shanghai's financial district, includes the world's third- and sixth-tallest buildings. The city's population is 23 million.

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Newborns lie together at a district women's hospital in Allahabad, in India's most populous state of Uttar Pradesh. Fifty-one babies are born in India every minute.

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Indian schoolchildren write English alphabets on slates at a primary school outside Hyderabad in June. India is on track to overtake China as the most populous nation in just 16 years. Noah Seelam/AFP/Getty Images hide caption

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Immigrants like these Indians at a Sikh festival in Barcelona are bolstering Europe's stagnant population growth rate. Randy Olson/National Geographic hide caption

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Sharing a hillside with high-rise apartment dwellers, children dance at a shop in one of the squatter communities that ring Caracas, a city of 3 million. Today, one in seven people live in slums. Providing them with better housing and education will be one of the great challenges facing a world of 7 billion people and counting. Jonas Bendiksen/Magnum Photos hide caption

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