In a time when the majority of the world was still lit by candle power, Nikola Tesla created the path for the electrical system known as alternating current, which to this day is what powers every home on the planet. On November 12th, 1896, at the Niagara falls the first hydro-electric powerplant of the world was inaugurated and put to work.
However this extremely creatively briliant man had many more ideas of which many were patented, some were stolen or absorbed by others (the radio by Marconi and in fact electricity itself by Edison) and many haven't even reached maturity or public notoriety. His lack of materialistic interest or money, unfortunately allowed or induced others to take advantage or abandon him, while he still had so much to develop and offer.
Charles Darwin teaches us the true story about the origin and development of life through his brilliantly intuitive theory of evolution. Against all evidence, this is, again and still, strongly opposed by fundamentalists of all religions.
Newton teaches us about the existence of gravity, offering the explanation on why we don't "fall" of the earth and how earth itself maintains its course around the sun, giving scientific support to what Colombo and Gallilei had already made clear trhough observation.
He also gave us the three fundamental laws of physics.
Some people think that Colombo's achievement was to "discover" a "new" continent. However his real achievement was to show and teach us that the earth is a globe and not flat, as was thought and insisted upon, throughout the retarded and supersticious Dark Ages in Europe.
The "discovery" of this "new" continent was actually no more than a mere coincidence due to miscalculation. Besides, he was not the first at all; Asians, Vikings and maybe even "Atlanticians" had already found it long before him. Some may argue that for the world, it might have been better if it would not have been re-discovered at all.