I.Reb Eliezer and Shimon Nodel are right. The neshameh emanates from God and since Hashem blew the neshameh into a person it is a part of Him that is in each person.
It is not only the neshameh, but the entire world is only God. Were God to desist His countantance from the universe it would cease to exist. We only exist because God Himself is granting chiyas, energy to everything in the universe. I myself do not understand this part, as is God Himself granting chiyas to evil? But yes, that is what it is because God is the source of all energy and matter.
So God is the source of life and therefore we are part of that Source, we are part of God. God is still One, One Being that is the Source of life.