Possibly the very first jet engine. Designed by Hero of Alexandria circa 100 A.D., the aeolipile consisted of a boiler, two tubes extending from the top of the boiler which attached to opposite sides of a metal sphere, the sphere itself, and two additional bent tubes attached to the sphere which were left open on the ends.

Fill the boiler with water, light a fire beneath, steam rises up through the tubes attached to the sphere and ultimately escapes through the bent tubes, causing the sphere to spin.

Supposedly, Hero employed this technology in a device which controlled the doors of the local temple.