He said to him, "Most assuredly, I tell you, hereafter you will see heaven opened, and the angels of God ascending and descending on the Son of Man."
Similarly a staircase makes travel and communication between two physical levels possible. Jesus was promising Nathanael that He would prove to be the key to access to God and communication with God (cf. John 14:6; 1 Timothy 2:5). God had revealed Himself to Israel, the man and the nation, in a dream at Bethel previously (Genesis 28:10-22). Now God would reveal Himself to a true Israelite, Nathanael, to all Israel, and to the world, directly through Jesus.