It's one thing to know that cities are growing larger, and that over half the human population lives in a city. But when you see these maps charting the growth of megacities since the early 1900s ... well, it's stunning. It's especially incredible when you realize most cities exploded in size over the past 50 years.

Map software company ESRI created a series of maps called "The Age of Megacities" to show how powerful data visualization can be when it comes to understanding our rapid urban growth.

Defining a megacity as an urban area with 10 million or more people, they note that the number of megacities in the world will grow from 28 to 41 over the next 35 years. Each map gives you a snapshot of a major global city over the past century, and as you click through each map layer, you can see tiny urban cores in the early 20th century become massive, land-consuming sprawls in 2014.

ESRI writes:

According to United Nations projections, the world will have 41 megacities within the next 35 years. The fastest growth is happening in Africa and Asia, where mid-sized cities are blossoming. By 2050, 66 percent of the world's population is expected to live in urban areas, and India, China and Nigeria will account for 37 percent of the anticipated growth.

We've got a few maps below, but you really must check out the whole collection over at ESRI.