Nicodemus came to Jesus by night, apparently because he was afraid that his peers might question him about why he came to see Jesus. He was a Pharisee and a ruler of the Jews and most of his peers hated Jesus because He didn't totally comply with their version of the law. He saw something different in Jesus and acknowledged that he knew He had come from God because otherwise he wouldn't be able to perform the miracles that He did. Jesus must have seen that he was troubled and anticipated his question because before he could even ask Jesus answered him. His response to the unasked question was that unless a man was born again he could not see the Kingdom of God. This puzzled Nicodemus, and he asked Him how a man could be born again, he couldn't enter into his mother's womb again. Jesus replied that he had to be born of water and of the Spirit. Nicodemus was still confused so Jesus tells him that He is going to be lifted up (die on a cross) and that whoever believed on him would not perish but have everlasting life.
When Jesus told him to be born again he had to be born of water and the Spirit, I was kind of confused as to what he meant by water, as we are not saved by being baptized in water. I asked the Lord for help to understand this and I believe this is what He showed me concerning the birth of a natural baby: "As the fertilized egg grows, a water-tight sac forms around it, gradually filling with fluid. This is called the amniotic sac, and it helps cushion the growing embryo." www.webmd.com
I believe that being born of water is our preparation period, a period of development we go through so we can be ready for and accept our new birth, some people readily accept, for others it takes a while. (Although water baptism doesn't save us Jesus does want us to follow his example of being baptized in water and I think I understand more about why now, not only does it represent our death, burial and resurrection, it also represents the time an embryo spends in it's mother's fluid till the time of it's birth, Romans 6:3 states that we are baptized into Jesus death, so his blood is like the fluid in the mother's womb that protects the embryo, when we come up out of the water (blood) it represents our new birth, it's not our salvation, it's a witness that we are saved.) Another possible answer is the one Jesus gave a Samaritan woman when He asked her for a drink, she was surprised because He was a Jew and they usually didn't have dealings with Samaritans. Jesus told her he could give her living water, and that anyone who drank that water would never thirst again, that it would be in that person a well of water springing up into everlasting life.
The following verse explains being born of the Spirit: You, however, are not in the flesh, but in the Spirit, since the Spirit of God lives in you. But if anyone does not have the Spirit of Christ, he does not belong to Him -Romans 8:9- The Holman Christian Standard Bible. Being born of the Spirit is accomplished by believing and accepting who Jesus is: the Son of God, the Word made flesh---the Son of man; why He came: that the World through Him might be saved; that He died for our sins, His sacrifice is the one and only payment for sin that God will accept, in other words He took our place, our deserved spiritual death; that He rose again, death and sin had no claim on him, he was perfect, had never sinned, he was able to cast off the sins and judgments of all who would believe in Him. Jesus told Nicodemus being born of the Spirit was like the wind blowing, you could hear it but you couldn't know where it originated from or where it ended up, in other words it had to be taken by faith.
This is a link to a site where you can look up scripture references in many different versions of the bible: http://www.biblegateway.com/