How was the steam engine invented? Who invented it?i just want to know about the invention.

The idea of using boiling water to produce mechanical
motion has a long history, going back about 2000 years. 

However, the
first practical steam-powered 'engine' was a water pump, developed in 1698 by Thomas
Savery. Then improving on the design of the 1712 Newcomen engine, the Watt steam engine
was developed sporadically from 1763 to 1775 and was the next great step in the
development of the steam engine. Then in around 1800, Richard Trevithick introduced
engines using high-pressure steam.

some
links

http://inventors.about.com/library/inventors/blsteamengine.htm

http://www.answers.com/topic/thomas-savery

http://www.answers.com/topic/history-of-the-steam-engine

http://www.answers.com/topic/steam-engine

http://www.answers.com/topic/watt-steam-engine

http://www.answers.com/topic/richard-trevithick