Jesus told Nicodemus, “You must be born from above.”
To explain how one might be born from above Jesus said, “The wind blows where it wills, and you can hear the sound it makes, but you do not know where it comes from or where it goes.”
There, Jesus said that there is a hidden world of prayer and grace that surrounds us. Unless we become part of that hidden world we cannot enter the kingdom of heaven.
Jesus gave Nicodemus and explanation of that hidden world. He compared it to the warm and cool air currents that move invisibly about us, affecting every aspect of our lives.
If Jesus were making the same explanation to Nicodemus today, he might use a more modern example to explain the movements of prayer and grace.
When I ride the bus to church mornings most of the people on the bus are making use of invisible sound waves. Some bus passengers have ear-phones for music on their I-Pods. A passenger here and there is engaged in a too-loud conversation with someone at home or the work-place. Another reads electronically transmitted books on a Kindle. They are electronically contacting the internet. When I am saying my Rosary on the bus I am prayerfully contacting heaven.