In my opinion and at Numero uno, is with out doubt Pierre and Madam Curie. There sheer hardwork, dedication, and application in extracting Radium from the ore Pitch Blend, in primitive conditions, illustrate the passion both had for the sciences. https://en.wikipedia.org/wiki/Marie_Curie There work is also excellently illustrated in a 1943 movie entitled "Madam Curie" with Walter Pidgeon and Greer Garson. Pierre was tragically killed in an accident, and Marie went on to win two Nobel prizes in different sciences...Physics and Chemistry. Number two in my opinion goes to Albert Einstein for obvious reasons, not the least being his humility. The rest goes without saying and is common knowledge.... Number 3 goes to a more recent scientist, Carl Sagan. Carl in my opinion was the greatest educator of our time, and probably is best remembered for his excellent series called Cosmos, released in the 70's and re made later with the permission of his wife Ann Druyan and narrated by Neil DeGrasse Tyson. Carl was also responsible for the actions of turning the cameras on the Voyager craft around to photograph Earth sitting like a moat of dust in a Sun beam, as well as placing a plaque on the craft in case it was discovered in the distant future by an Alien species. Carl also while accepting the fact that we probably are not alone, also debunked the many cases of Alien piloted UFO's. Some honourable mentions; Edwin Hubble: For his discovery of the expansion of the universe. Sir Issac Newton: For the first explanation of gravity. Stephen Hawking: Like Madam and Pierre Curie, Hawking achievements were done despite the great personal afflictions he had. A true marvel. All personal choices of course.