The technology to make nuclear weapons has become easier to get and easier to hide, scientists have been caught trading in nuclear secrets, and many say the treaties written to stop the spread of warheads around the globe are now out of date.

Nature news tells the story of how we ended up at this nuclear 'tipping point', where our actions in the next few years will determine whether we sink into a second wave of nuclear proliferation. Our reporters dig into the politics behind nuclear ambitions in the Middle East and visit stockpiles of fissile material in Russia now under lock and key. And we canvass the arms-control community to find out how bad the current situation is; and how nuclear materials can be kept in check.