Born again and Eternal life

John 2:24-3:21
Jesus would not entrust himself to them, for he knew what was in a man.
Pharisees named Nicodemus, a Jewish ruling council, he came to Jesus at night ad said," Rabbi, we know you are a teacher who has come from God."
Jesus declared,"I tell you the truth, no one can see the kingdom of God unless he is born again."
Jesus answered,'I tell you the truth, no one can enter the kingdom of God unless he is born of water and the Spirit." The Spirit like wind blows wherever it pleases, you hear the sound, but you cannot tell where it comes from or where it is going.
Jesus said," I tell you the truth, we speak of what we know and we testify to what we have seen, but still you people do not accept our testimony.
Whoever believes in him is not condemned, but whoever does not believe stands condemned already because he has not believed in the name of God's one and only Son.
Light has come into the word, but men loved darkness instead of light because their deeds were evil. But whoever lives by the truth comes into the light, so that it may be seen plainly that what he has done has been done through God.
John's only used of "kingdom of God", the phrase so frequently used in the other three Gospel. "Eternal life" he use constantly.
Why?
Eternal life involves something which can only be described as rebirth, being 'born of the Spirit'
How?
I am born in of water and Spirit, bu sometime I have my flesh mind, may holy Spirit get rid of my selfish mind, think more about the things of heaven.