Regeneration is the work of the Spirit of God that renews the current state into a better state of being, In the same sense that salvation is in the can be divided into three parts, just the creation and the creation and the creation. So regeneration has three parts in that regeneration we use as the spirit of God, He is continuing to regenerate us as we live the journey of this life and we will be regenerated fully when we stand before Him.
Titus 3:5
not by righteous works we have done, but according to His mercy, by which He saved us, through the washing of regeneration and renewing of the Holy Spirit.
Matthew 19:28
And Jesus said to them, “I say to you rightly, in the regeneration, when the Son of Man sits on the throne of His glory, those who've followed Me, will also sit on twelve thrones, judging the twelve tribes of Israel.