The steam turbine
A steam turbine is a mechanical device that converts heat from pressurised steam into a rotary motion. Iinvented in 1884 by the Englishman Sir Charles Parsons, it has a greater thermal efficiency and higher power-to-weight ratio than the piston-based steam engine that it has almost completely replaced. About 80% of all electricity generation in the world today uses steam turbines.
A very early steam turbine was the aeolipile described in the 1st century by Hero of Alexandria; in 1551 AD the Turkish polymath Taqi al-Din described the workings of a rudimentary steam turbine in The Sublime Methods of Spiritual Machines.
Relation to Power:
The creation of the modern steam turbine opened the way to electricity as a practical power source. With cheap power easily available in more places than was possible even with the steam engine, dramatic changes throughout the whole of society became possible including longer working hours thanks to relatively safe electric lighting, the introduction of automation to the home, and ultimately electric and later electronic computers that would drive yet further changes in the way we live, think and work.
Read more about the steam turbine on Wikipedia.