Donald Trump says one of the first things he'll do when he becomes president is deport up to 3 million undocumented immigrants. It would be one of the largest such roundups in American history.
Here are answers to many questions about how he will accomplish that.
How many "criminal" undocumented immigrants are there?
In a post-election interview with CBS' 60 Minutes, Trump said he would deport 2 million to 3 million of the 11 million undocumented immigrants who are "criminal and have criminal records." The actual number depends on how one defines "criminal."
The Migration Policy Institute, a non-partisan think tank, estimates 820,000 undocumented immigrants have been convicted of a crime in the United States. About 300,000 were convicted of felonies and 390,000 of serious misdemeanors.
The Department of Homeland Security puts the number of "removable criminal aliens" at 1.9 million, but that estimate includes foreigners with legal status, people convicted of all crimes (except for traffic offenses) and those repeatedly caught crossing the border.
Many are already in custody, making them the easiest to identify. The Congressional Research Service estimates more than 142,000 non-citizens were in federal and state prisons and local jails in 2013, the last year for which data is available. The service could not determine how many were undocumented.
How will the government track down those undocumented immigrants?
Trump could ask Congress for more funding to increase the size of Immigration and Customs Enforcement (ICE), but a quicker solution would be redirecting the current 14,000 ICE officers, agents and special agents to concentrate on arrests.
But only 1,000-1,100 agents currently track down fugitive undocumented immigrants who are criminals or gang members, according to John Sandweg, a former acting director of ICE. The rest work on detention operations, screening visa applicants in foreign countries, conducting immigration audits of U.S. businesses and investigating crimes that include money laundering, import and export fraud, and human trafficking.
Sandweg said several core functions must be maintained because of congressional mandates, but an ICE director could easily refocus more people to finding undocumented immigrants.
"There would be a lot of flexibility for an ICE director to re-calibrate the agency," said Sandweg, now an attorney with Frontier Solutions.
How quickly can undocumented immigrants be deported?
Before they can be deported to their home country, immigrants have the right to a hearing before an immigration judge. But the nation's immigration courts are already overburdened.
That has led to a huge backlog of 521,676 cases waiting nearly two years on average to be heard, according to the Transactional Records Access Clearinghouse at Syracuse University. Cases take an average of 675 days to complete, with some states like Colorado averaging more than 1,000 days per case.
The only way to speed up those cases is to hire more immigration judges. There are currently 273, according to the Justice Department. Congress has approved funding to increase the number to 374, and Trump could ask Congress to hire even more.
Yet, even if Trump filled all 374 posts and added 150 more judges over the next two years, they could not clear out all the currently pending immigration cases until 2023, according to a review by Human Rights First, a non-profit advocacy group.
Which undocumented immigrants will be targeted?
Trump's emphasis on criminals may leave millions of other undocumented immigrants in the clear.
One such group: the 740,000 young undocumented immigrants granted deportation protections under President Obama's Deferred Action for Childhood Arrivals program, known as DACA. To qualify, they had to register with the federal government, have a clean record and work or go to school.
Trump has vowed to end the program and rescind their deportation protections, leaving them fearful of being targeted.
Mexican nationals would be the most heavily targeted, because they account for 52% of undocumented immigrants, according to the Pew Research Center. Another 15% come from Central America, 13% are from Asia, and 6% come from South America.
Deported Mexicans are usually sent home by bus, while those from other countries are put on flights.
What will happen to those who remain?
As a candidate, Trump often hinted that some undocumented immigrants could remain in the U.S. During the 60 Minutes interview, he said that after the border is secured, his border wall is completed and "everything gets normalized," he would "make a determination" on how to handle those who remain.
Trump has not elaborated, but Republican proposals in recent years provide some possibilities.
In 2014, after the Senate passed a bill that allowed some undocumented immigrants to become U.S. citizens, House Republicans outlined a plan that instead would let them receive legal status, but not citizenship.
Immigration advocacy groups decried the House proposal as "second-class citizenship," but some Republicans endorsed that idea as a way to punish undocumented immigrants for entering illegally but still allow them to live in the U.S. without fear of deportation.