John 1:47-51 You will see greater things

⁴⁷ When Jesus saw Nathanael approaching, he said of him, “Here truly is an Israelite in whom there is no deceit.”
⁴⁸ “How do you know me?” Nathanael asked.
Jesus answered, “I saw you while you were still under the fig tree before Philip called you.”
⁴⁹ Then Nathanael declared, “Rabbi, you are the Son of God; you are the king of Israel.”
⁵⁰ Jesus said, “You believe because I told you I saw you under the fig tree. You will see greater things than that.” ⁵¹ He then added, “Very truly I tell you, you will see ‘heaven open, and the angels of God ascending and descending on’ the Son of Man.”

If someone you had never met started talking to others who were standing nearby, about what a great person you were, you’d probably be as curious as Nathaniel, wouldn't you?
Nathanael asked, "How do you know me?"
There are two different Greek words that both mean "to know."  One refers to general knowledge,and the other refers to stronger knowledge, like that of a person who has experienced something first hand, or has personal acquaintance with someone. So, Nathanael wanted to understand how Jesus could know him so well, having never met him before.
Philip and the others probably exchanged knowing glances, for they were certain they knew the reason. They were certain that Jesus was the Christ, the Messiah for whom they had waited, and for Him to have this kind of knowledge was just another proof.

It's interesting to see that Jesus says, "I saw you under the fig tree." There are three other times that this phrase is used in the Bible. If you would like to check them out, look at I Kings 4:25, Zechariah 3:10, and Micah 4:4.  Here is one of them for an example:

 During Solomon’s lifetime Judah and Israel, from Dan to Beersheba, lived in safety, everyone under their own vine and under their own fig tree. I Kings 4:25

Each time the phrase is used, sitting under the fig tree is a symbol. It's a symbol of a life of peace and blessings, which come from an obedient relationship with God.
It's not such a shocker for us, I guess, because we live in an age of satellites and surveillance! And, we are assured of the Spirit of God living with us each day -- but for Nathanael it was different. He knew now that he was dealing with someone whose knowledge was profound and divine.  So he declared, "Rabbi, you are the Son of God; you are the King of Israel."
Jesus also told him, "You will see greater things than these." After commending him for being obedient to God, He is calling Nathanael into a deeper relationship.
We know that the more we allow Jesus to be the center of our lives, the more we have of His peace in our hearts.

In the last verse of our passage, Jesus addresses not just Nathanael, but all of those gathered around Him.

"He added, 'I tell you the truth, you (plural) shall see heaven open, and the angels of God ascending and descending on the Son of Man.'"

The commentaries tell us that Jesus is referring to Genesis 28, which would have been so familiar to His listeners. In that excerpt of the life of Jacob, Jacob was fleeing his brother Esau. He was sleeping outside, and God gave him a comforting dream: a staircase from earth to heaven, with angels going up and down on it. Jesus' words to his followers seem to indicate that He is referring to that passage, and He is saying that He is the staircase.
Jesus is the one through whom we have access to heaven! He bridged the gap for us -- His life was the only one that met the standards of God's law. His cross has bridged the gap between God and sinful humans, and removed the sin-barrier that stood between us and God the Father.
What an amazing thing for Nathanael to consider! No wonder he was taken by surprise. Not only did Jesus demonstrate how well He knew Nathanael, but He also demonstrated that He was the long-awaited Messiah; He was the One who would show us "greater things" and make us fit for heaven!