STORY: Iran and the United States swapped five detainees each on Monday (September 18), thanks to a Doha-brokered deal between the arch foes.
The move also saw $6 billion of Tehran's funds unfrozen.
But how did this come to be, what does the deal look like, and what happens next?
A Reuters source says the swap was triggered after Qatar confirmed that the frozen funds had been transferred to bank accounts in Doha.
Under the deal, five Americans with dual nationality left Tehran for Doha, before heading to the U.S.
In return, five Iranians held in the U.S. have been released.
The detained Iranian Americans who will be allowed to leave Iran include two businessmen, 51-year-old Siamak Namazi and 59-year-old Emad Shargi, and 67-year-old environmentalist Morad Tahbaz, who also has British nationality.
The other two prisoners have not been identified.
Iran's mission to the United Nations says the five Iranians to be released by the U.S. are Mehrdad Moin-Ansari, Reza Sarhangpour-Kafrani, Amin Hassanzadeh, Kambiz Attar-Kashani, and Kaveh Afrasiabi.
The agreement was borne out of months of diplomatic contacts, secret talks and legal maneuvering.
Qatar has been at the heart of negotiations throughout, sources and officials say.
Since March 2022, Doha has hosted several rounds of indirect clandestine meetings between Tehran and Washington.
Early talks focused heavily on Iran's nuclear dispute with the U.S..
But over time, shifted to detainees, as negotiators realized nuclear discussions would lead nowhere due to their complexity.
In September, Washington waived sanctions to allow the transfer of Iran's funds to Qatari banks.
Doha will now take on a monitoring role to ensure Iran's rulers spend the funds on non-sanctioned goods.
Iran's funds had been frozen in South Korea, normally one of Iran’s largest oil customers, after U.S. sanctions on the Islamic Republic were hardened in 2018.
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The move came after then-U.S. President Donald Trump's decision to ditch Tehran's 2015 nuclear deal with six world powers.
Hostility to the U.S. has always been a rallying point for Iran's clerical establishment.
That's despite it suffering political isolation and sanctions-related economic hardship since Washington severed ties shortly after the 1979 Islamic revolution.
Supreme Leader Ayatollah Ali Khamenei could likely tolerate some limited civility between Iran and the U.S., amid growing public anger over severe economic challenges.
But Iranian insiders say normalizing ties with Washington would likely be a step too far.
Clerical leaders fear improved relations could weaken the legitimacy of the Islamic Republic and its influence in the region - as well as harming Khamenei's domestic authority.
The transfer of Iran's funds has drawn Republican criticism that U.S. President Joe Biden, a Democrat, is in effect paying ransom for U.S. citizens.
The White House has defended the deal.
Whether it leads to future agreements regarding Iran's nuclear standoff with the U.S. remains unclear.