Hero of Alexandria invented a simple steam turbine in about 130BC, but it could only spin itself it couldn't drive another mechanism.
Thomas Savery invented the first primitive steam engine used to pump water out of coal mines.
Thomas Newcomen improved Savery's design so that it used atmospheric pressure and no longer depended on the limited steam pressure of boilers of the time.
James Watt improved Newcomen's design by condensing the steam in an external condenser instead of the cylinder, leaving the cylinder always hot reducing thermal cycling stress and dramatically raising efficiency.
