Despite decades of growth, demand for more and faster internet connections continues to skyrocket. According to Cisco, total internet traffic for 2016 will exceed a zettabyte. (A one with 21 zeroes behind it.) That’s enough capacity to stream approximately 143 billion hours of Netflix video at Ultra HD quality.

Though demand is concentrated in the most developed countries, much of the world’s internet growth is driven by globe-spanning enterprises. Companies such as Facebook, Google, and especially, Netflix are pushing the limits of how much content can be shuttled around the world each day. Though satellite connections also exist, the vast majority of intercontinental traffic crosses a relatively small number of undersea cables—the arteries of the global internet.

The map above, created with data from Telegeography, shows how those cables have developed since 1990. Most existing cables were constructed during a period of rapid growth in the mid-2000’s. This was followed by a gap of several years during which companies steadily exhausted the available capacity. Over the last few years, explosive new demand, driven by streaming video, has once again jumpstarted the the construction of new cables.

Most cables are laid by consortiums of providers that work together to fund the projects and to negotiate with the countries where the cables “land.” Typically the largest members of these groups are major internet providers, such as Level 3 and Verizon. However, according to a Telegeography report (pdf), many cables under construction today are receiving significant funding from internet giants Facebook, Google, and Microsoft. Those companies now consume so much bandwidth that they require dedicated connections across the ocean.