Today, world leaders are hoping to finally come to an agreement over Iran's nuclear programme.
Representatives for the UK, US, China, Russia and Germany have met with Iran in Lausanne, Switzerland, to try and persuade it to curb its nuclear enrichment programme in return for an easing of economic sanctions.
Iran has been accused of trying to build a nuclear weapon, but denies this and says everything it's doing is for civilian purposes.
The issue has been ongoing for a long time – attention was first drawn to it in 2003 by an inflammatory report by the International Atomic Energy Agency (IAEA), and a number of deadlines for an agreement were missed last year. This time was no different – the official deadline was yesterday, but the talks have been pushed into today.
The main framework of the plan is to get Iran's enrichment low enough that it would take more than a year for the country to build a weapon, and earlier today Russian Foreign Minister Sergei Lavrov said "one can say with relative certainty that we at the minister level have reached an agreement in principle on all key aspects of the final settlement of this issue". He has now left the talks.
So what exactly is Iran doing to make the rest of the world so wary of its nuclear activities? Here's a breakdown
Highly enriched uranium
Enriched uranium is used by many countries for civilian purposes, such as producing energy and electricity. For these harmless useless, enrichment tends to take place at 3.5 per cent.
But if it is concentrated enough, it can be taken to the next level and used to create a nuclear bomb. That's why it caused alarm when Iran was discovered to be holding onto a stock of 20 per cent enriched uranium, which is considered very close to weapons-grade.
Some headway has been made with this in negotiations – last summer, Iran agreed to dilute its highly enriched uranium to five per cent. However, this is still above the average and considered by many as unnecessary for civilian use.
Too many centrifuges
Iran has around 18,000 centrifuges, 10,000 of which are currently spinning. This is a very large number – much larger than in most countries – and other nations are trying to persuade Iran to bring the number down to 6,000.
Centrifuges are dangerous because they are essentially the building blocks for creating nuclear weapons. The tube-shaped machines are able to convert natural uranium into a highly enriched version using a centrifugal force.
Although these by their very nature are not known about, it is thought that Iran could be developing nuclear weapons at secret sites.
IAEA inspectors have access to all of Iran's declared nuclear facilities, but they are fighting for more – they want to be able to travel throughout the country and have access to any facility they want. This is one of the main points being discussed at the talks.
There are definite grounds for suspicion – Iran has by no means always revealed its nuclear sites to inspectors, and some of the sites known about today were previously kept secret.