Iran's key nuclear sitesArak - Heavy water plant
The existence of a heavy water facility near the town of Arak first emerged with the publication of satellite images by the US-based Institute for Science and International Security in December 2002.
Heavy water is used to moderate the nuclear fission chain reaction either in a certain type of reactor - albeit not the type that Iran is currently building - or produce plutonium for use in a nuclear bomb.
In August 2010, the IAEA visited the IR-40 heavy water reactor site at Arak. It said the facility was still being built but some major equipment had been installed. Iran told the IAEA the operation of the reactor was planned to start by the end of 2013.
The IAEA said that based on satellite imagery, the heavy water production plant appeared to be in operation, but had not had access to it to confirm such reports.Bushehr - Nuclear power station
Iran's nuclear programme began in 1974 with plans to build a nuclear power station at Bushehr with German assistance.
The project was abandoned because of the Islamic revolution five years later, but revived in the 1990s when Tehran signed an agreement with Russia to resume work at the site.
Moscow delayed completion on the project while the UN Security Council debated and then passed resolutions aimed at stopping uranium enrichment in Iran.
In December 2007, Moscow started delivering the canisters of enriched uranium the plant needs.
Earlier in the same month, a US intelligence report said Iran was not currently running a military nuclear programme.
There are two pressurised water reactors at the site.
Satellite images from March 2010 show the first completed reactor building on a site that occupies 2.5 square kilometres (one square mile), about 17 km (11 miles) south of the city of Bushehr.
Iranian state media said the plant was connected to the national grid in September 2010.
When it was inspected by the IAEA in October 2011, the agency noted that the reactor was in operation.Gachin - Uranium mine
In December 2010, Iran said it had delivered its first domestically produced uranium ore concentrate, or yellowcake, to a plant that can make it ready for enrichment.
Iran's nuclear chief Ali Akbar Salehi said the first batch of yellowcake had been sent from Gachin mine sent to a conversion facility at Isfahan.
Mining operations started at the Gachin in 2004.
Iran was believed to be running low on its stock of yellowcake, originally imported from South Africa in the 1970s.Isfahan - Uranium conversion plant
Iran is building a plant at a nuclear research facility to convert yellowcake into three forms:
- Hexafluoride gas - used in gas centrifuges
- Uranium oxide - used to fuel reactors, albeit not the type Iran is constructing
- Metal - often used in the cores of nuclear bombs. The IAEA is concerned about the metal's use, as Iran's reactors do not require it as fuel.
Iran resumed uranium enrichment work at Natanz in July 2004, after a halt during negotiations with leading European powers over its programme.
It announced in September 2007 that it had installed 3,000 centrifuges, the machines that do the enrichment. In 2010, Iran told the IAEA Natanz would be the venue for new enrichment facilities - construction of which would start around March 2011.
This is the facility at the heart of Iran's dispute with the United Nations Security Council.
The Council is concerned because the technology used for producing fuel for nuclear power can be used to enrich the uranium to a much higher level to produce a nuclear explosion.Parchin
One area at Parchin has been identified as a suspected nuclear weapons development facility.
The overall complex is one of Iran's leading munitions centres - for the research, development and production of ammunition, rockets and high explosives. A limited inspection carried out by the IAEA in 2005 found no proof of any nuclear weapons activity at Parchin.
But according to information from an IAEA report in November 2011, it is believed the site has also been used for testing high explosives that could be used in nuclear weapons.Qom - Uranium enrichment plant
In January 2012, Iran said it had begun uranium enrichment at the heavily fortified site of Fordo near the holy city of Qom.
It had revealed the existence of the facility, about 30km (20 miles) north of the city, in September 2009.
Iran initially informed the IAEA that it was constructing the plant to produce uranium enriched up to 5% - commonly used in nuclear power production.
In June 2011, Iran told the IAEA that it was planning to produce uranium enriched up to 20% at Fordo - and would subsequently stop 20% fuel production at Natanz.
In January 2012, the IAEA confirmed Iran had started the production of uranium enriched up to 20%.
Iran says the Highly Enriched Uranium (HEU) is for use as a fuel in research reactors. Uranium - with a concentration of 20% or more - is needed to build nuclear weapons.
The IAEA says environmental samples taken from the site at Fordo in April 2011 did not indicate the presence of enriched uranium.