Roots of the Nephilim
There is enigma contained within the lines of Genesis 6, for its appears to embody two entirely different traditions.
Look at Genesis 6:2 :
Gn:6:2: That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose.
They speak of the Sons of God coming unto the Daughters of Men, while in contrast with Genesis 6:4 :
Gn:6:4: There were Giants (in Hebrew bible Nephilim) in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.
The meaning seemed clear enough: A fallen race known to the early Israelites as the Nephilim (mentioned elsewhere in the Pentateuch as the progenitors of a race of Giants called Anakim, (Josh 14:12). The children of the ‘bene ha-Elohim’, the Sons of God, who are equated directly with the Angels of God in Jubilees tradition and the Watchers in Enoch tradition.
The Amorite was said to be as tall as the cedar, ie. 30 – 40 feet tall. (see Amos 2:9)
A giant footprint in South Africa shows we are not talking about mere myths and fables
This irruption of fallen angels before Noah’s day was probably Satan’s first attempt to prevent the coming of the “Seed of the woman” foretold in Genesis 3:15. If this could be accomplished, God’s Word would have failed, and Satan’s own doom would be averted.
Genesis 3:15 KJV
And I will put enmity between thee and the woman, and between
thy seed and her seed; it shall bruise thy head, and thou shalt
bruise his heel. (Also see Isaiah 7:14)
Note it says speaking to the serpent ‘your seed’. When did Satan have children? It could only be these giants?
Coercion Code - "Dark Times are upon us" 
We believe the entire Bible. I wrote years ago (on line) that they could not have been angels. Angels do not procreate, as Jesus taught. So much teaching one has heard all one’s life has turned out to be incorrect. This shows how eagerly, diligently and thoroughly we should read our Bibles – in context.
Irene,
This wickedness of fallen angels was what corrupted ALL flesh.
There appears some genetic contamination into our humanity that these ones like Nimrod became excessively large and wicked.
The very reason God gave the human race 120 years before destroying all but 8 individuals with the flood.
Genesis 3:15 KJV
And I will put enmity between thee and the woman, and between
YOUR seed and her seed; it shall bruise thy head, and thou shalt bruise his heel. (see isaiah 7:14.