No matter what we know of God, there's more. No matter how long we've walked with Jesus, there's a greater understanding to which we are called.
This wisdom and knowledge are forms of maturity. The Ephesian church was to arrive at this maturity via "a spirit of wisdom and revelation in the knowledge of Him."
However, in an attempt to not over-spiritualize a thing we must recognize that God gives us a spirit of revelation via many seemingly natural ways: His inspired word, his appointed teachers, etc.
The Apostle Paul says as much in Ephesians chapter 3. Writing to Gentile Christians, Paul speaks of his stewardship of God's grace. He goes on to say that what was given to him by way of revelation (both supernatural and via hearing what the other Apostles taught) was given to be written down and read by the people in Ephesus.
In their reading of Paul's revelation verse 4 says that they could then understand Paul's insight into the very same mystery. Mind you this is the mystery of Christ, and it's a mystery that other generations were not privy to either.
In Ephesians chapter 1 we read several of the mutual revelations Paul and the people had.
First, God is a God of blessing. This idea is found in verse 3. However, God was not just a God of blessing but One that had blessed us with every spiritual blessing in the Heavenly places in Christ.
Second, they knew that God was a God of standards. In verse 4, scripture says, "God chose us in Christ Jesus before the foundation of the world that we would be holy and blameless before him."
Finally, they knew that God was a God of love. In verse 4 it says, "In love, God predestined us to adoption as Sons." God didn't want mere servants, but he predestined us to be Sons.
There are many more things that we can find in Ephesians chapter 1:1-15. I want to encourage you to read and discover for yourself these mysteries of God.