According to Genesis 2:7 the substance of our bodies is

Genesis 2:7

"Then the LORD God formed a man from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being."

This biblical passage refers to the fact that the main substance by which the human being was created is the dust. There is another passage in the bible (Genesis 3:19) which says "for dust thou art, and unto dust shalt thou return." also making reference that God created the human being from dust, giving him breath of life.