Today's Gospel is John's story of the call of Nathanael (presumably the same as Bartholomew in the other Gospels). Evidently there is a great unstated "given" in this story, because the turning point comes when Jesus tells Nathanael "I saw you under the fig tree." This provokes an outpouring of awed faith on Nathanael's part that has left people wondering for 2,000 years, "What on earth happened under the fig tree?"
Fig trees (and the leaves thereof) are pretty important in the Bible. In general, reference to a person's "vine and fig tree" hinted at peace and modest prosperity. Especially peace. And under a fig tree, the peaceful, modestly prosperous property owner could sit in the shade and meditate on God's goodness. So we presume that Nathanael was doing something of the kind, and in that shady place of prayer found that, not only was Nathanael contemplating God's goodness, God was, in a way, contemplating Nathanael. And then along comes this Jesus, son of Joseph from Nazareth who says, in effect, "Uh, that was me."
The Gospel also has some interesting language about sight. Philip invited the skeptical Nathanael "Come and see." That's close to the invitation Jesus extended to Andrew and the other disciple who had asked where he was staying: "Come and see." But while Philip used the verb form for "behold," John depicts Jesus using a word that the Bible often reserves for visions of God--for sight that is "bestowed."
And, finally, today's Gospel is situated in a part of John (Chapter 1) that gives us practically a litany of titles for Jesus, all culminating in Nathanael's profession of faith:
John the Baptist calls him "the Lamb of God."
Andrew says he is "the Messiah."
Philip calls him "the one Moses and the prophets wrote about."
and Nathanael exclaims "you are the Son of God! You are the King of Israel!"
And in the Bible, the only real King of Israel is the Lord God himself.
Jesus, meanwhile, insists on calling himself only "Son of Man." It is as if in his Incarnation he chose to identify more with us than with God.