(CNN) The journey of Americans released from Iran is far from over.
From the future of U.S.-Iranian relations to the fate of another missing American, Sunday's release could mark just the beginning of more political maneuvering to come.
Here's the latest on the prisoner swap and what's next:
Which Americans were freed in the swap?
Washington Post journalist Jason Rezaian, Marine veteran Amir Hekmati, Christian pastor Saeed Abedini and Nosratollah Khosravi-Roodsari were released as part of a prisoner swap.
Iran detained Rezaian in 2014, eventually charging him with espionage and other crimes, according to The Washington Post. He was the newspaper's Tehran bureau chief.
Hekmati was detained in 2011, weeks after arriving in Iran to visit his grandmother, according to his family's website. The former Marine infantryman and Arabic and Persian linguist was accused of espionage and other charges in 2012.
Abedini, an Iran native and convert to Christianity, was arrested in 2012 and convicted the next year on charges of attempting to undermine the Iranian government. He had been sentenced to eight years in prison.
Not much is known about Khosravi-Roodsari.
Iran prisoner swap: 14 months of secret diplomacy
Who else was released?
Matthew Trevithick, a student who was recently detained, was also released -- but not as part of the prisoner swap. He arrived Sunday night in Boston, according to his stepmother, Susan Trevithick.
U.S. officials indicated to Iran's foreign minister "that it'd be important for them to try to resolve some of the other cases of Americans detained in the context of this" deal, a senior administration official told CNN.
Where are they?
Rezaian, Hekmati and Abedini arrived Sunday at Ramstein Air Base in Germany, and they were scheduled to undergo medical checkups at Landstuhl Regional Medical Center, a U.S. military hospital.
Hekmati's family released a photo Monday showing him with two sisters and a brother-in-law along with U.S. Rep. Dan Kildee, D-Michigan. They spent about 15 minutes together, according to a brief statement from the family.
The Washington Post's Jason Rezaian, left, reunites with his family in Germany.
The Washington Post released a photo of Rezaian, showing him and family members smiling broadly.
The Americans' flight from Iran was delayed for a time due to confusion over the whereabouts of Rezaian's wife and mother, whom U.S. officials had insisted be part of the release deal. On Monday, U.S. Secretary of State John Kerry said in an interview with CNN's "New Day" that Iran's foreign minister and other officials understood the terms of the agreement included the two and ensured it happened.
"All's well that ends well," he said.
Khosravi-Roodsari decided not to leave Iran, senior White House officials said. "It's his free determination" whether he wants to stay in Iran, one official said. "We don't make that judgment."
What happens next?
It's unclear how long the medical evaluations would take, but the former prisoners met with friends and family Monday.
The American Center for Law and Justice, a Washington-based group dedicated to protecting religious and constitutional freedoms, reported that Abedini was tortured during his imprisonment and beaten by fellow prisoners in June. He suffered injuries to his face at the time, the center reported.
Hekmati suffered from health problems, including weight loss and breathing difficulties, according to his family.
Jared Huffman, who represents Rezaian and has been involved in his case, said the journalist, Hekmati and Abedini won't be on U.S. soil for a few days.
Jason Rezaian's brother, Ali Rezaian, told CNN on Monday that his sibling is "in good spirts" and excited about getting out and seeing people, but first has to "focus on getting better."
Jason Rezaian's brother: Iranians 'continued to manipulate' until very end
What did Iran get in return?
In exchange for the American prisoners' freedom, Washington pardoned or commuted the sentences of an Iranian and six dual citizens of the United States and Iran in what President Barack Obama called a "one-time gesture."
The men allegedly had been involved in exporting products and services to Iran in violation of trade sanctions against the country. They were accused of exporting goods ranging from electronic components and satellite services to marine navigation and military equipment to Iran.
Khosrow Afghahi, Tooraj Faridi, Bahram Mechanic and Nima Golestaneh were pardoned. Nader Modanlo, Arash Ghahreman and Ali Saboonchi had their sentences commuted, the U.S. Justice Department said.
The United States also agreed to drop charges against 14 other Iranians whose extradition seemed unlikely, a U.S. official said.
On Monday, Iranian Foreign Ministry spokesman Hossein Jaberi Ansari said that 28 Iranians "were freed or were relieved of judicial restrictions" under the agreement.
He did not name them.
Who are the Iranian prisoners released in the swap?
Did the nuclear deal play a role?
The announcement of the prisoners' release came as the U.N. nuclear watchdog, the International Atomic Energy Agency, announced Sunday that Iran is in compliance with a July deal to restrict its nuclear program.
As a result, at least some international economic sanctions against Iran were lifted.
The prisoner swap came after more than a year of secret negotiations, officials said.
Kerry has said the nuclear agreement "accelerated" the prisoner exchange, but he told CNN on Monday that talks on the nuclear deal were on a "separate track" from the swap.
GOP 2016 hopefuls slam Obama's policy
Is Iran holding any other Americans?
Americans detained abroad
Kim Dong Chul, a South Korean-born American citizen detained in North Korea, is escorted to his trial April 29 in Pyongyang. A North Korean court sentenced Kim to 10 years in prison for what it called acts of subversion and espionage. North Korea watchers interpret the detainment of Americans and other foreign citizens as a collection of bargaining chips by the reclusive regime.
University of Virginia student Otto Frederick Warmbier was detained by North Korea after being accused of carrying out "a hostile act" against the government, state media reported. In March, he was sentenced to 15 years of hard labor for allegedly removing a political banner from a Pyongyang hotel.
Jason Rezaian, The Washington Post's bureau chief in Tehran,
was released January 16 as part of a prisoner swap. Rezaian
was convicted by an Iranian Revolutionary Court in October, according to Iran's state-run media. Rezaian was reportedly facing up to 20 years, but the sentence was not specified. The journalist was taken into custody in July 2014 and later charged with espionage; the Post has denied all allegations against him. His wife, Yeganeh Salehi, also was detained in July 2014 but later released.
Saeed Abedini, a U.S. citizen of Iranian birth, was
freed as part of a prisoner swap that included Washington Post journalist
Jason Rezaian on January 16. Abedini was
sentenced to eight years in prison in January 2013. He was accused of attempting to undermine the Iranian government and endangering national security by establishing home churches. He was detained in Iran on September 26, 2012, according to the American Center for Law and Justice.
Amir Hekmati, a former U.S. Marine charged with spying, was
freed as part of a prisoner swap that included Washington Post journalist
Jason Rezaian on January 16. An Iranian court threw out a 2011 death sentence for
Hekmati, but he was secretly retried in Iran and convicted of "practical collaboration with the U.S. government," his sister told CNN on April 11. He was sentenced to 10 years in prison, she said. Hekmati was detained in August 2011 during a visit to see his grandmother. His family and the Obama administration deny accusations he was spying for the CIA.
Siamak Namazi, a Dubai-based businessman with dual U.S. and Iranian citizenship, was
detained while visiting relatives in Tehran, the Wall Street Journal reported October 29, citing unnamed sources. The Washington Post also reported his detention, citing a family friend who spoke on condition of anonymity. The Post reported that it wasn't clear what Namazi is alleged to have done. His detention would bring to five the number of Americans detained or unaccounted for in the Islamic republic.
Scott Darden was
taken hostage by Houthi rebels in Yemen in March 2015. He was captured while working for New Orleans-based Transoceanic Development, according to a source close to his family.
Retired FBI agent Robert Levinson
has been missing since 2007. His family says he was working as a private investigator in Iran when he disappeared, and multiple reports suggest Levinson may have been working for the CIA. His family told CNN that they have long known that Levinson worked for the CIA, and they said it's time for the government to lay out the facts about Levinson's case. U.S. officials have consistently denied publicly that Levinson was working for the government, but they have repeatedly insisted that finding him and bringing him home is a "top" priority.
The FBI increased its reward for information on Levinson from $1 million to $5 million.
Mothers Linda Boyle, left, and Lyn Coleman hold photo of their married children, Joshua Boyle and Caitlin Coleman, who were kidnapped by the Taliban in late 2012. Coleman was pregnant when she was kidnapped and is believed to have had a child in captivity.
Jailed since 2013 and sentenced to life for supporting the Muslim Brotherhood in Egypt, Mohamed Soltan
was eventually released, the U.S. Embassy in Cairo said in May 2015. Soltan's family denies he belonged to the Brotherhood. Soltan had been a dual U.S. and Egyptian citizen, but he renounced his Egyptian citizenship as a condition of his release.
One of three Americans detained in North Korea, Jeffrey Edward Fowle was released and sent home, a State Department official told CNN in October 2014. Fowle was accused of leaving a Bible in a hotel where he was staying. North Korea announced Fowle's detention in June of that year, saying he had violated the law by acting "contrary to the purpose of tourism." Fowle told CNN: "I've admitted my guilt to the government and signed a statement to that effect and requested forgiveness from the people and the government of the DPRK."
In May 2013, a North Korean court sentenced Kenneth Bae, a U.S. citizen, to 15 years of hard labor for committing "hostile acts" against the state. North Korea claimed Bae was part of a Christian plot to overthrow the regime. In a short interview with CNN in September 2014, Bae said he is working eight hours a day, six days a week at a labor camp. "Right now what I can say to my friends and family is, continue to pray for me," he said. After months in detention, he and fellow American detainee Matthew Todd Miller were
released in November.
Miller, an American sentenced to six years of hard labor in North Korea, was one of three Americans who spoke to CNN's Will Ripley in September 2014 and implored the U.S. government for help. The 24-year-old was accused of tearing up his tourist visa and seeking asylum upon entry to North Korea.
American journalist Peter Theo Curtis was
handed over to U.N. peacekeepers in August 2014 after nearly two years in captivity. He is believed to have been captured in October 2012 and held by the al-Nusra Front, a Syrian rebel group with ties to al Qaeda.
Alan Gross, at right with Rabbi Arthur Schneier, was jailed while working as a subcontractor in Cuba in December 2009. Cuban authorities say Gross tried to set up illegal Internet connections on the island. Gross says he was just trying to help connect the Jewish community to the Internet. Former President Jimmy Carter and New Mexico Gov. Bill Richardson both traveled to Cuba on Gross' behalf. He was eventually
released in December.
This undated image provided by the U.S. Army shows Sgt. Bowe Bergdahl, who had been held by insurgents in Afghanistan since 2009. The White House
announced Bergdahl's release on May 31, 2014. Bergdahl was released in exchange for five senior Taliban members held by the U.S. military. In March 2015,
the U.S. military charged Bergdahl with one count each of "Desertion with Intent to Shirk Important or Hazardous Duty," and "Misbehavior Before The Enemy by Endangering the Safety of a Command, Unit or Place."
U.S. tourist and Korean War veteran Merrill Newman arrives at the Beijing airport on December 7, 2013, after being released by North Korea. Newman was
detained in October 2013 by North Korean authorities just minutes before he was to depart the country after visiting through an organized tour. His son Jeff Newman said the Palo Alto, California, man had all the proper paperwork and set up his trip through a North Korean-approved travel agency.
Mexican authorities arrested Yanira Maldonado, a U.S. citizen, right, in May 2013, for alleged drug possession. She and her husband, Gary, were traveling from Mexico back to the United States when their bus was stopped and searched. She was released a few days later and is now back in the United States.
North Korea has arrested Americans before, only to release them after a visit by a prominent dignitary. Journalists Laura Ling, center, and Euna Lee, to her left, spent 140 days in captivity after being charged with illegal entry to conduct a smear campaign. They were
freed in 2009 after a trip by former President Bill Clinton.
Former President Jimmy Carter
negotiated the release of Aijalon Gomes, who was detained in 2010 after crossing into North Korea illegally from China. Analysts say high-level visits give Pyongyang a propaganda boost and a way to save face when it releases a prisoner.
Detained in April 2011, Eddie Yong Su Jun
was released by North Korea a month afterward. His alleged crime was not provided to the media. The American delegation that
secured his freedom included Robert King, the U.S. special envoy for North Korean human rights issues.
Without any apparent U.S. intervention, Robert Park was released by North Korea in 2010. The Christian missionary crossed into North Korea from China, carrying a letter asking Kim Jong Il to free political prisoners and resign. North Korea's state-run news agency said
Park was released after an "admission and sincere repentance of his wrongdoings." Here, Park holds a photo of Kim and a malnourished child during a protest in Seoul.
Josh Fattal, center; Sarah Shourd, left; and Shane Bauer were detained by Iran while hiking near the Iraq-Iran border in July 2009. Iran charged them with illegal entry and espionage. Shourd was released on bail for medical reasons in September 2010; she never returned to face her charges. Bauer and Fattal were convicted in August 2011, but the next month they were
released on bail and had their sentences commuted.
Haleh Esfandiari, an Iranian-American scholar, was detained at Iran's Evin Prison, spending months in solitary confinement before
Iran released her on bail in August 2007. Esfandiari was visiting her ailing mother in Tehran when she was arrested and charged with harming Iran's national security.
Sixteen Americans were among the dozens arrested in December 2011 when Egypt raided the offices of 10 nongovernmental organizations that it said received illegal foreign financing and were operating without a public license. Many of the employees posted bail and left the country after a travel ban was lifted a few months later. Robert Becker, right,
chose to stay and stand trial. He spent two years in prison and has since returned to the United States.
Filmmaker Timothy Tracy
was arrested in Venezuela in April 2013 on allegations of funding opponents of newly elected President Nicolas Maduro, successor to the late Hugo Chavez. Tracy went to Venezuela to make a documentary about the political division gripping the country. He was released in June 2013.
During negotiations, another American's name was apparently on the table: Robert Levinson.
Iran has denied holding Levinson, a former FBI agent and CIA contractor who went missing there in 2007.
Now the agreement between the United States and Iran calls for Iranian officials to "continue cooperating with the United States to determine the whereabouts of Robert Levinson," a U.S. official said.
Kerry said Sunday that Iran had agreed to deepen coordination in the search.
"We are happy for the other families," Levinson's family said in a statement. "But once again, Bob Levinson has been left behind. We are devastated."
Details on detained, missing Americans
CNN's Frederik Pleitgen, Brian Stelter and Catherine E. Shoichet contributed to this report.