In the beginning, before even time began, there was only God and Nothing.
For God to know God was not enough. God wanted to experience his supreme Godhead, infinite goodness and his supreme power..
To experience the full extent of Goodness one must also experience evil. To experience hot you also need to experience cold otherwise hot is meaningless. In other words you must also experience both ends of the spectrum to have the full experience.
However, the Almighty God ran into a problem. He had to un-god God to experience evil, weakness, sickness, misunderstanding, diseases and so on. Since God cannot un-god God. He came up with a brilliant plan.
He created the spiritual and physical universe. He also created Man. He allowed evil to exists and made Man imperfect, so that Man and experience both good, evil, disease, weakness, jealousy, anger, and so forth.
Now God feels everything including what Man feels. In this way, God can experience everything including his Supreme Goodness and Power through his creations which includes Man. So both God and Man is on a holy mission on God's great plan.
Now no one needs nothing to make anything. You can only make something out of something else. So God created everything with himself. He became every atom, photon, energy, and every thing else. He is the Great Seen and Unseen. He is Everything there ever was, is, and will be forever and ever. There is nothing else. In a sense, he is even not what he is. Even evil cannot exist without God. To the Greeks everything can be represented by the term "Alpha and Omega". Actually it should be the Alpha and Omega and all in between. This meaning was lost in translation. Therefore God is everything in other words the "Alpha and Omega".