Truly, truly (Greek amēn amēn): Jesus often used this phrase to emphasize important points. In John’s Gospel, the Greek word amēn is always doubled.
you will all see heaven open: Jesus made the comparison with Jacob clear (see study note on 1:47; see Genesis 28:10–22). Like Jacob, Nathanael would see God at work. Jacob saw a vision at Bethel, where God revealed himself (Genesis 28:19).
Jesus himself is the new Bethel. The name Bethel means “house of God.” In other words, Jesus is the place where God now lives among his people.
Son of Man: See study note on John 9:35; see also Daniel 7:13–14; Mark 8:31.
John the apostle used several names for Jesus (Son of God, Son of Man, Christ). Knowing the true identity of Jesus is necessary to fully understanding and following him.