Berndnaut Smilde makes clouds. The Dutch artist has devised a way to combine water vapor with smoke to create miniature clouds that hover in enclosed spaces. He’s been deploying it in locations ranging from cathedrals to coal mines.

“I see them as temporary sculptures, made of almost nothing, balancing on the edge of materiality, an image of prospect in an empty space,” he told Rajesh Punj. “For me the work is about the idea of a cloud inside a space and what people project onto it. You can see them as a sign of misfortune or an element from a classical painting. There is something ungraspable about clouds: it might explain why people have been projecting so many meanings and myths upon clouds for centuries.”

Time named the technique one of the 50 best inventions of 2012.