Shenzhen and Hong Kong are two major economic powerhouses just twenty miles apart. Thousands of cars and people cross their borders every day. But their close relationship belies inequalities that still exist between the city of Shenzhen and the Special Administrative Region of Hong Kong.

"One Country, Two Lungs" is a project by the MIT Senseable City Lab and LAAB that aims to visualize these inequalities through one index: air pollution. Roving researchers—essentially, human bots crawling for data—carried air quality sensors as they commuted through Shenzhen and Hong Kong. Their preliminary data for carbon monoxide, nitrogen dioxide, and tiny dust particles known as particulate matter are visualized in mesmerizing red, yellow, and green hues in the video above. So far, the air quality in Shenzhen seems worse, possibly owing to the huge factories that have contributed to the city's recent boom.

The name of the project harkens to "One Country, Two Systems," the slogan coined to describe Hong Kong as it would be governed following the transfer of its sovereignty back to China from the United Kingdom. The city is part of China now, but as a Special Administrative Region. Shenzhen and Hong Kong remain, as the project description puts it, "distinct but interconnected atmospheres."

The two cities are separated not only by geographic border on the ground, in other words, but also by an invisible, atmospheric one. Each city has its own associated mass of air, with its characteristic smells, humidity, and levels of particular matter. But they do occasionally overlap and mix, swirled together by wind patterns or made permeable by pockets of air carried back and forth in cars and in the lungs of commuters. [One Country, Two Lungs]