By 2015, there will be 58 cities on the planet with a population of 5 million or more and, by 2025, according to National Intelligence Council, 27 cities with a population exceeding 10 million. The U.N. Population Division classifies populations in excess of 10 million as megacities and many of these urban behemoths will be located in the so-called 10/40 window—the area in Africa and Asia between north latitude 10 and 40 degrees. This emerging growth will have serious consequences for international stability, human security and environmental degradation. Without a doubt, unchecked growth in the 10/40 window will change the face of the global map in the twenty-first century. The questions are: how and what should be done about it? In this article, we primarily address the how question—leaving a detailed examination of policy options to others, as we contend that the most important step at this point in time is to first understand the nature of the problem.