By analogy each adult human life can be compared to an "egg" or "ovum." This "ovum" has a very limited life span - an average of about 70 years - compared to eternal life. But spiritual, divine immortal life may be imparted to it by God the Father.
As the physical male sperm finds its way to and unites with the nucleus in the ovum, so God's Spirit enters and combines with the human spirit in man! This happens upon receipt of the Holy Spirit - after real repentance, baptism, and the laying on of hands of a true minister of God. One thus begotten by the Spirit of God is now a "babe in Christ" (I Corinthians 3:1). He is already a child of God, though yet unborn. By direct analogy the embryo in a mother's womb is already the child of its parents, though not yet born.
A spirit-begotten child of God now has the presence of eternal life - God life - through God's Spirit, but he is not yet an immortal spirit being - not yet born of God - not yet an inheritor and possessor. He is merely an "heir" with Christ (Romans 8:17). The divine life of God has merely been begotten.
This divine life and character starts so very small in one it is doubtful if much of it is in evidence - except for the glow of that ecstasy of spiritual "romance" which one may radiate in that "first love" of conversion, spiritually speaking. But so far as spiritual knowledge and developed righteous character goes, there is not much - yet.
Once spiritually begotten, we are merely a spiritual "embryo." Now we must be fed and nourished on spiritual food so we can grow spiritually! Jesus said man shall not live by bread (physical food) alone, but by every word of God (spiritual food)! This we take in from the Bible. Our spiritual growth and development of God's righteous character also comes through personal, intimate, daily contact with God through prayer, through Christian fellowship with other Spirit-begotten children in God's church, and also by the spiritual teaching imparted by the church.