The Guardian is reporting that a "secret annex" the IAEA's recent report on Iran's nuclear program describes the significant progress the Iranian have made toward building an implosion nuclear warhead (for you visual learners, here is a gif):

The annexe said Iranian scientists had engaged in "probable testing" of explosives arranged in a hemisphere, which is how an implosion-type nuclear warhead is triggered.

There was also evidence, the report says, that Iran had worked on developing a chamber to carry a warhead on top of one of its missiles "that is quite likely to be nuclear".

This news should of course be taken with some caution. In the coming weeks, information and disinformation campaigns regarding Iran's capabilities and intentions will make it hard to decipher which reports are valid and which are well placed leaks.