It’s not a bird. Not a plane. It’s a flying microchip.

It’s a clear fall morning, and sycamore seeds are spiraling to the ground.

Something gleams in the air. You trap it between your fingers, and peering closely, you see that it’s not a seed or a speck of dust, but a winged microchip — about the size of a grain of sand. After you marvel at the ingenuity, you wonder what it’s for.

All kinds of things, potentially, says John Rogers, a professor at Northwestern University’s McCormick School of Engineering and Applied Science.

Rogers was the lead scientist on the project to develop the “microflier” — the smallest-ever, man-made flying structure, according to Northwestern. Its story and possible applications are chronicled this week in the journal “Nature.”

Rogers said he and and his team drew inspiration from the natural world, observing how seeds float down from trees and other plants, and are dispersed over a wide area.

Rogers envisions the microfliers being dropped, possibly in the tens of thousands, from an airplane or a drone and used to detect, say, air pollution. The information could be transmitted back to a computer for analysis, he said.

Interestingly, the technology exists to make far smaller microfliers.

“The problem is: below about 1 millimeter, everything just falls like a sphere. You loose all of the aerodynamics that lead to gliding and helicopter motion,” Rogers said.

The microfliers are just in the lab phase of development, but Rogers envisions the cost to make a single one would be negligible — about a penny. And he envisions them being made out of materials that would dissolve in water and not create additional pollution.

The fliers could be dropped into rivers, lakes and — even the oceans — to detect for the presence of heavy metal contamination, Rogers said.

“The ideas are new, and I’m sure other people have created other ideas we haven’t thought about,” he said.