Issac Newton was once asked how he had managed to accomplish so much.
He said
"If I have seen further it is by standing on ye shoulders of Giants." 5 Feb. 1676

A Similar quote: "I see far because I stand on the shoulders of giants." - Albert Einstien suggest the same thing which recognizes the contributions of our predecessors.

Those "Giants" whose shoulders we all stand on are people who have made a significant contribution to Humanity,

They are not necessarily Physically Larger than the rest of us. For example: Mother Teresa was a very short Giant.

Giants can appear at any time in human history.

Giants can appear in any place in the world.

Giants can be of any background or culture.

Giants can be any one who is willing to do what they think is Right. Even if others Do Not support or Agree with them.