Amen, amen, I say to you, unless one is born from above, he cannot see the kingdom of God. Jesus’ conversation with Nicodemus, the first of the Johannine discourses, continues the self-manifestation of Jesus begun in the second chapter when Jesus performed his first sign (the wedding at Cana). In the passage we have read today, Jesus, through the mouth of Nicodemus, is revealed both as being indwelt by God and as having come from God. Nicodemus’ recognition of Jesus’ divine origins rested on Jesus’ working of signs (Nicodemus must have been aware of some other signs performed by Jesus in addition to the changing of water into wine). In response, Jesus proceeded to talk about the need to be born again as a requisite to belonging to the kingdom of God. The signs he was performing and which Nicodemus had rightly pointed out as proof to his divine origins were evidence that the kingdom of God had indeed been inaugurated. The train had already left the station and everybody needed to be on board since it is only those who are on board who can see the signs and interpret them accordingly. 
To be born again is to realign oneself on the side of God (we come from God but our sins turn us away from God). It is only when we are born again that we are enabled not only to  seeGod acting concretely in the world but also to make that presence felt. It is she/he who has realigned the self with God who can work towards the realization of peace, justice, and respect for creation. The mighty signs that Jesus was performing and which Nicodemus recognized were possible because Jesus was with God.