Who invented the first steam engine?

During the first century AD, a Greek inventor and mathematician called Hero of Alexandria produced a device that later led to the development of modern turbines and jet engines. Hero's device was a hollow water-filled ball mounted on a swivel. Two nozzles stuck out of opposite sides, pointing in different directions. When the ball was heated, steam shot out of the nozzles, causing the ball to spin rapidly.

Hero failed to see the practical use of this device and regarded it as an interesting toy. He went to invent several mathematical formulae, one of which is still used for calculating the area of the triangle.