The Bible says in Genesis 1:27 that "God created man in his own image, in the image of God created he him; male and female created he them." Yes, man man was created in the very image of God. What does that mean? The word in Hebrew is "tselem" and it means to shade, a phantom, illusion, icon, resemblance or a representative figure. In English there is an old expression that we use when someone looks like someone else: spitting image (e.g., he is the spitting image of his father).
Now, that does not mean that we necessarily look like God, for no one knows what God looks like (John 1:18). Instead, it means that we were made in his image. Remember that we are a representative figure. God is a trinity in that he is God the Father, God the Son, and God the Holy Spirit. In other words, there is one God expressed in three eternal and coequal persons. We get an insight into this when it says in Genesis 1:26, And God said, "Let us make man in our image, after our likeness."
Yes, the trinity is indeed hard to understand, and even harder to explain. However, I will make an attempt using the properties of H2O, or what is commonly referred to as water. Water can exist in three different states: solid, liquid, and gas, and yet the chemical make up, H2O, never changes. It is still water. So too, the Trinity never loses its identity as God.
With that said, how are we in God's likeness? Simple, we are a trinity just as God is a trinity. I like to express it this way, God is the mind of the Godhead, the Son is the body of the Godhead, and the Holy Spirit is the spirit of the Godhead. Man also has a mind, body, and spirit. We see this confirmed in 1 Thessalonians 5:23 when Paul said, "And the very God of peace sanctify you wholly; and I pray God your whole spirit and soul (mind) and body be preserved blameless unto the coming of our Lord Jesus Christ." We are indeed made in the image of God!