"Now there was a man of the Pharisees, named Nicodemus, a ruler of the Jews; this man came to Jesus by night and said to Him, "Rabbi, we know that You have come from God as a teacher; for no one can do these signs that You do unless God is with him." Jesus answered and said to him, "Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God." (Jn. 3:1-3).
Here's the original "Nick at night" who can say what he sees, but can't see what Christ says. Maybe if Jesus were talking to a Roman soldier who had very limited knowledge of Israel's God or a first year scribe in divinity school, but a ruler of the Jews, a leader of the Sanhedrin -- all of which underscore three crucial points of the new birth.
First, what it says about our human condition -- dead. Birth assumes a starting point, the beginning of an existence, not a blending, merging or developing of something already there. Jesus doesn't tell Nicodemus he needs to further his education, rehabilitate his blindness, raise his consciousness, deepen his commitment, or re-work his 12-step program. He doesn't even tell him how to get born again. Seeing the miraculous isn't the same as seeing the Kingdom.
Second, what it says about our "birth control" -- none. "The wind blows where it wishes" (vs. 8). We didn't cause our physical birth, neither can we cause our spiritual one. If the free, sovereign, uncoerced Spirit of God doesn't give life, all the religious and charitable activities of the flesh not only profit nothing, but actually hinder those who seek the help of such activities (Gal. 4:29).
Third, what it says about God's work -- life. What is born of the Spirit is spirit, not part spirit and part flesh, and once born can't be unborn or die (Phil. 1:6). This new creation (2 Cor. 5:17) comes with a guaranteed inheritance (1 Pet. 1:3-4), a righteousness-practicing ability (1 Jn. 2:29), a world-overcoming strength (1 Jn. 5:4), a sin-killing violence (Rom. 8:13), a devil-destroying triumph (1 Jn. 5:18), culminating in a death-defeating victory (1 Cor. 15:54-57). Those who possess this life own all things on earth and hold title to all authority in heaven (Eph. 2:6). This life can't be taken by or shared with others, and its presence holds societies together (Matt. 5:13ff.) while its prayers shape their future (1 Tim. 2:1-2; Rev. 8:3-5).
Poor Nick -- he's in over his head. He receives the signs but can't receive the witness (Jn. 3:11). Cadavers who claim to see shouldn't be surprised when they trip over non-existent vital signs.