Pentecost is often referred to as the birthday of the church. It is the moment in the Book of Acts where the disciples are transformed from a group sequestered in an upper room, to a movement ready to reach out to the entire world. Only the Holy Spirit can make this change. He is our power; the power Jesus promised, and the power we need to be Christ-ians, or little Christs.
God the Spirit often seems like the most confusing Person in the Trinity; yet He is as close to us as the air we breathe.