Who first discovered steam power?

The ancient Greek mathematician and engineer Hero of Alexandria is often credited as the first inventor of a device fueled by steam power – the aeolipile – described almost two thousand years ago in c.50 AD. However, the real pioneers of what was eventually to become steam engine technology did not appear until the middle of the 17th century when scientists of the Scientific Revolution such as Denis Papin (1647-1712) began experimenting with steam pressure.