President Donald Trump says the US has carried out a "successful" bombing attack on three nuclear sites in Iran and said they have been "obliterated".
Israel says they were in "full co-ordination" with the US in planning the strikes. Iranian officials have confirmed the facilities were struck but denied it had suffered a major blow.
The strikes mark a significant escalation in the ongoing war between Iran and Israel.
So what happens now? Here are the key questions, answered by our world news correspondent Joe Inwood.
Video journalists: Sofia Ferreira Santos and Tom Joyner