Oneness and unity is an interesting charecteristic of the Spirit. Where there is Spirit, there is unity, but the absence of the Spirit brings in conflicts and diversity.
The unity that comes from the Spirit shows in our own Body, then this earth, then the solar system, then this whole universe, which stands as one single body. From a small micro organism to the big large universe there is unity in every entity that God has made. The unity of Spirit is not restrictied to just within a body, when a man and woman get united in Spirit they become a family, and when members of church unite they become the Body of Church, when we unite with Christ in spirit we become Body of Christ. The unity that is brought by the Spirit has no barrier. It can overcome all physical barriers and reach out to unite.
God made Adam from dust, then He blew His breath (the Spirit) into him and Adam became man. When the Spirit leaves, men return to dust. It is the Spirit when unites this whole body and keeps the body live, active and moving. It hurts when the unity in Spirit breaks. The existence of Spirit is revealed only when it breaks and hurts. The interesting part is there is unity even among the people who are atheists. There is unity among the rebels. There is unity among the people who try to break unity. There is no limitation to what or how the Spirit can unite us. There are no boundaries to the Unity in Spirit. That makes the Presence of God the most challenging definition.
The Word of God defines it very clear, that you know the seed by its fruits. Galations 5:22-23 But the fruit of the Spirit is love, joy, peace, forbearance, kindness, goodness, faithfulness, gentleness and self-control. Against such things there is no law. (NIV)
Jesus Christ by dying on the Cross, He gives us the Holy Spirit which reunties us with the Everlasting Love of God and aboundant Grace and forgiveness, that it can unite us in the Church, in the community, at work, in knowledge, in wisdom, in strength, in body, in love, in hope, in faith.