Iran election: How the vote happens
Nearly 50 million people are eligible to vote in the elections in Iran - almost 70% of them from the capital, Tehran, and big cities. Only 30% of voters come from rural areas.
There are nearly 70,000 polling stations in the country, and according to the authorities nearly a million people are involved in the process - making sure all goes smoothly.
All a voter needs in order to vote is his or her birth certificate, which is stamped once they have voted.
Voters make their choice by writing the name of their preferred candidate in a box.
The ballot paper carries at the top a slogan by the leader of the 1979 revolution and the first Supreme Leader of the Islamic Republic of Iran, Ayatollah Ruhollah Khomeini, which reads: "What matters is the vote of the people."
Underneath, the ballot says: "Dear compatriot, please print the name and the surname of the candidate of your choice with his candidacy number in the space provided below."
After a person has voted, they have to press their thumbs onto an ink pad to ensure they cannot vote again.
Illiterate voters are helped by staff in the polling station - a procedure which has often caused speculation and accusations of irregularities. The vote is monitored by observers from the Interior Ministry, the body in charge of holding the elections.
There are also observers from the Guardian Council, as well as representatives of the candidates. But not all candidates have enough representatives to cover all polling stations.
There are also mobile polling stations - buses with ballot boxes which visit prisons, hospitals and so on. They are a source of concern for many as they are a difficult to keep under observation.
There are no independent or foreign observer missions - Iran does not allow this. The results are reported by fax to the interior ministry's election headquarters, where they will be added up before being released on live television.
In 2009, there was a widespread perception that the authorities at the so-called "addition room" of the interior ministry manufactured millions of votes in favour of President Mahmoud Ahmadinejad.
Iranians will be trying to watch the counting process very carefully this time.