This rural-to-urban migration can now be seen in scores of cities around the globe. And it has brought us to a pivotal moment in human history. In 1900, most people lived in the countryside, with a little over 10 percent of the world’s population living in cities. From next year, the UN Population Division predicts that for the first time in history, more people will live in cities than in the country, and the biggest growth will be in “megacities,” with populations over 10 million.