By Jim Sciutto and Ben Brumfield, CNN
The diplomatic gridlock between Iran and the West seemed immovable for decades. But on Sunday, diplomats made history when Iran and six world powers came together on an agreement over Iran's nuclear program.
The deal dials back Iran's ability to work toward a nuclear weapon and at the same time loosens the choke hold of international sanctions on Iran's economy.
The two sides now have six months to find out how historic the breakthrough really is. That's the duration of the preliminary agreement hammered out in Geneva, Switzerland, by Iran and the P5+1 - the five permanent members of the U.N. Security Council plus Germany.
"There are lots of things, regrettably, that we still have to work on. Our hope is that Iranian President Hassan Rouhani and Foreign Minister Javad Zarif want to build this different relationship, want to show in clear ways as we go forward that the program is peaceful," U.S. Secretary of State John Kerry told CNN's "State of the Union."