That which is born of the flesh is flesh, and that which is born of the Spirit is spirit.
(John 3:6)
And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever; Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
(John 14:16-17)
For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit. For to be carnally minded is death; but to be spiritually minded is life and peace. Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be. So then they that are in the flesh cannot please God.
But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his. And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness.
(Romans 8:5-10)
Christ is not talking about a floating ball of light you can photograph or put in a jar, and Paul isn't writing about something that is omnipresent floating around in the air all over the earth - as though it were dust in the air. it is something that the world cannot see, because the world sees with eyes made out of flesh, which is like grass, rising out of dust, blooming for a little while and then turning back into dust.
but how great is our God! how great is our redemption in Christ!
Thy dead men shall live, together with my dead body shall they arise.
Awake and sing, ye that dwell in dust:
for thy dew is as the dew of herbs, and the earth shall cast out the dead.
(Isaiah 26:19)