In most encounters Jesus had with Pharisees, they were trying to catch he and his followers breaking some law or tradition. But Jesus always had a response to their accusations and questions which sent them away pondering the situation from the standpoint of maintaining mercy over sacrifice, love over law.
The fact that Nicodemus came seeking Jesus during the darkness of night should be noted. Nicodemus probably would not be meeting with the favor of his fellow Pharisees if they had known he was on such friendly terms with Jesus. Then, what he says to Jesus is also going to be problematic in the understanding and actions of most Pharisees. Nicodemus confessed that he knew Jesus was a teacher from God, because no one could do the things Jesus was doing if God were not with him.
That's when Jesus broke the news, "No one can see the kingdom of God unless they are born again." Born when they are old? We can understand him not being able to understand that. A grown man cannot enter the womb of his mother a second time to be born again.
Jesus explains, "No one can enter the kingdom of God unless they are born of water and the Sprit. Flesh gives birth to flesh, but the Spirit give birth to spirit." He uses the illustration of the wind blowing, and we know it does, but we cannot explain it. Even though we can hear the sound of it, we cannot tell where it comes from or goes. Notice the final sentence, "So it is with everyone born of the Spirit."
Our first birth brings us into our earthly family. Our second birth brings us into God's family. We do not make the choice to be born into our physical lives. The second birth is by our choice. When we are born the first time, we are a citizen of earth. Our second birth gives us citizenship in heaven.
Those who are born of the Spirit still live in this world, but their hearts and minds are focused on a new plane, a new way of life, a life on the journey to eternity. It involves complete surrender of our will to the will of God, allowing God to change us to become more and more like Jesus. New birth means new life. "No one can see the kingdom of God unless they are born again."