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.

Visiting Thomas Povey in 1663, Samuel Pepys was surprised when his host opened a door to reveal an unsuspected region of the house.

At a second glance he saw that Povey had only opened a closet in which a large deceiving painting had been hung.

The painting, Samuel Dirksz van Hoogstraten’s View of a Corridor, still hangs at Dyrham Park today.

Dark Matter (2014), by the artistic collaborative Troika, manages to be a circle, a hexagon, and a square all at once.

The same group had created Squaring the Circle a year earlier.

American furniture artist Wendell Castle’s 1978 Chair With Sports Coat is really neither — it’s an eye-deceiving sculpture carved from maple.

The Waiter, by Italian painter Giuseppe Arcimboldo, circa 1574.

Is it a still life or a portrait?