Who invented steam engines and when?

Hero of Alexandria, a Greek engineer, and mathematician who lived in the 1st century AD, invented the first steam engine. His device, called the Aeolipile, was a hollow sphere with two nozzles that allowed steam to escape, causing the sphere to spin rapidly.

However, it was Thomas Savery who invented the first practical steam engine in 1698. His engine was used for pumping water out of mines. The Savery engine was followed by Thomas Newcomen's steam engine in 1712, which was more efficient and could be used for a wider variety of tasks.

Finally, in 1769, James Watt invented the first truly efficient steam engine. Watt's engine used a separate condenser to cool the steam, which dramatically improved its efficiency. Watt's engine paved the way for the Industrial Revolution and transformed the world economy.