When the people of God pray~heaven is moved! WOW...that is pretty powerful stuff! I have been studying session two of the Bible study "When God's People Pray" and it is truly overwhelming when you still yourself long enough to internalize the fact that God's Holy Spirit dwells inside His people and helps us to pray what we ought.
In the same way, the Spirit helps us in our weakness. We do know what we ought to pray for, but the Spirit himself intercedes for us through wordless groans.