Christ in us: The Mystery of God

See how the apostle Paul explains this mystery:

This is how he explained it in one city:
I became its minister according to the responsibility given me by God to present to you fully the word of God, the mystery that was hidden for ages and generations, but has now been revealed to his saints. To them God chose to make known among the Gentiles the glorious riches of this mystery, which is Christ in you, the hope of glory. Col 2:25-27

Then in another:
My children, I am again suffering birth pains for you, until Christ is formed in you. Gal 4:19

And again in another city:
I strive that they may be strengthened in their hearts, united in love, and reach all the riches of full understanding, so that they may fully know the mystery of God, namely, Christ. In him are hidden all the treasures of wisdom and knowledge. Col 2:2-3

And now, how do you see this mystery?