No one knows the essence of God. Quoting St. Gregory Nazianzen, St. Gregory of Nyssa, and St. John Damascus in order:
(1) "Far before them is That nature Which is above them, and out of which they spring, the Incomprehensible and Illimitable — not, I mean, as to the fact of His being, but as to Its nature... For it is one thing to be persuaded of the existence of a thing, and quite another to know what it is. God would be altogether circumscript, if He were even comprehensible in thought: for comprehension is one form of circumscription... The Divine Nature cannot be apprehended by human reason, and that we cannot even represent to ourselves all its greatness."
(2) "For we say, it may be, that the Deity is incorruptible, or powerful, or whatever else we are accustomed to say of Him. But in each of these terms we find a peculiar sense, fit to be understood or asserted of the Divine nature, yet not expressing that which that nature is in its essence. For the subject, whatever it may be, is incorruptible: but our conception of incorruptibility is this — that that which is, is not resolved into decay: so, when we say that He is incorruptible, we declare what His nature does not suffer, but we do not express what that is which does not suffer corruption. Thus, again, if we say that He is the Giver of life, though we show by that appellation what He gives, we do not by that word declare what that is which gives it."
(3) "It is plain, then, that there is a God. But what He is in His essence and nature is absolutely incomprehensible and unknowable. For it is evident that He is incorporeal... But even this gives no true idea of His essence, to say that He is unbegotten, and without beginning, changeless and imperishable, and possessed of such other qualities as we are wont to ascribe to God and His environment. For these do not indicate what He is, but what He is not. But when we would explain what the essence of anything is, we must not speak only negatively. In the case of God, however, it is impossible to explain what He is in His essence, and it befits us the rather to hold discourse about His absolute separation from all things... God then is infinite and incomprehensible and all that is comprehensible about Him is His infinity and incomprehensibility. But all that we can affirm concerning God does not show forth God's nature, but only the qualities of His nature. For when you speak of Him as good, and just, and wise, and so forth, you do not tell God's nature but only the qualities of His nature."
This is why St. Paul says we will know as we are known and see clearly God then, not that we will contain Him, but that through divine grace we will "behold" His essence, for to see and to see all or to know of and to know of all are obviously distinct (as we shall know completely according to our capacity as created beings but God knows us completely according to His capacity as uncreated, which is infinite), quoting St. Paul:
"For now we see through a mirror indirectly, but then face to face. Now I know in part, but then I will know completely, just as I have also been completely known."
The indirect nature of this being shown by the Fathers above, how that works in detail. God if He is infinite (and we know ourselves to be finite) by definition His essence can not be "circumscribed" or limited by our thoughts or complete comprehension.