Colossians 1:19-20

For God was pleased to have all his fullness dwell in him, and through him to reconcile to himself all things, whether things on earth or things in heaven, by making peace through his blood, shed on the cross.

God was pleased
Ephesians 1:5 ... he predestined us to be adopted as his sons through Jesus Christ, in accordance with his pleasure and will--

to have all his fullness dwell in him
John 1:16 From the fullness of his grace we have all received one blessing after another.
Colossians 2:9 For in Christ all the fullness of the Deity lives in bodily form.

to reconcile to himself all things
Romans 5:10 For if, when we were God's enemies, we were reconciled to him through the death of his Son, how much more, having been reconciled, shall we be saved through his life!
Romans 8:19-22 The creation waits in eager expectation for the sons of God to be revealed. For the creation was subjected to frustration, not by its own choice, but by the will of the one who subjected it, in hope that the creation itself will be liberated from its bondage to decay and brought into the glorious freedom of the children of God. We know that the whole creation has been groaning as in the pains of childbirth right up to the present time.

whether things on earth or things in heaven
Ephesians 1:10 ... to be put into effect when the times will have reached their fulfillment--to bring all things in heaven and on earth together under one head, even Christ.

by making peace
Luke 2:14 "Glory to God in the highest, and on earth peace to men on whom his favor rests."

through his blood, shed on the cross
Ephesians 2:13 But now in Christ Jesus you who once were far away have been brought near through the blood of Christ.

NOTES:
Genesis 3:15, 17-19

Scriptures taken from the Holy Bible, New International Version® NIV®, Copyright© 1973, 1978, 1984 by International Bible Society. Used by permission. All rights reserved worldwide.