Probably the most difficult concept for us to really understand is the triune existence of God the Father, God the Son, and God the Holy Spirit. I try to help us grasp this concept.
Scriptures to aide in understanding:
Col 1:19, John 14:9, Acts 3:15, John 1:1-3,14, Philippians 3:1-6, John 10:38, 17:11,21, 14:11