You can't explain what is going on inside that seed to make it grow and produce a crop. You just know it does. The seed can be dissected and placed under a microscope but there is nothing there that tells you why it grows. There is nothing that tells how the spirit of life dwells in that seed. You just know it does, because it is alive.
Spiritual growth is as mysterious as the coming and going of the wind.
Flesh gives birth to flesh, but the Spirit gives birth to spirit. The wind blows wherever it pleases. You hear its sound, but you cannot tell where it comes from or where it is going. So it is with everyone born of the Spirit. James tells us, if we need wisdom, we must ask God for he gives wisdom to all liberally.