The phrase Standing on the shoulders of giants is a metaphor which means “Using the understanding gained by major thinkers who have gone before in order to make intellectual progress”.It is a metaphor of dwarfs standing on the shoulders of giants (Latin: nanos gigantium humeris insidentes) and expresses the meaning of “discovering truth by building on previous discoveries”. This concept has been dated to the 12th century, according to John of Salisbury is attributed to Bernard of Chartres. But its most familiar and popular expression occurs in a 1675 letter by Isaac Newton: “If I have seen further it is by standing on the shoulders of Giants.”
Source:Wikipedia