The growth of these so called "instant cites" has provided great opportunity, but they also pose enormous challenges, problems and risks. One such city is Karachi in Pakistan. A city that sits not only in a center of development, but also straddles the geopolitical fault lines of its region.
The co-host of NPR's Morning Edition, Steve Inskeep, has been traveling to Karachi since 2002 and has witnessed its growth up close and personal. In his first book, Instant City: Life and Death in Karachi, he takes us inside Karachi as a model of this migration that is changing the world.
My conversation with Steve Inskeep: