Washington (CNN) President Donald Trump made history Sunday when he became the first sitting US president to enter North Korea.

During the brief visit to the hermit nation, which came after the end of the G20 summit in Japan , Trump shook hands with North Korean leader Kim Jong Un before the two met for nearly an hour at the demilitarized zone between the two Koreas.

While the encounter lacked the pomp and circumstance of the leaders' second meeting last year, there were several memorable moments from Sunday's unprecedented event.

Trump went where no sitting US president has gone before

Trump took 20 steps that no other sitting US president has taken.

While on North Korean soil, Trump and Kim shook hands and patted each other's backs before returning across the border after about a minute.

"I never expected to meet you at this place," a seemingly overjoyed Kim told Trump through an interpreter.

Trump said he was "proud to step over the line."

US and North Korea are restarting talks, Trump says

After crossing into North Korea, Trump and Kim held a private bilateral meeting inside the Freedom House at the DMZ for just under an hour.

Trump said he agreed with Kim to restart staff-level talks that had fallen apart after their last summit in February. There did not appear to be any new commitments made in the 50-minute meeting beyond the revived talks.

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Trump said negotiating teams would begin meeting in a matter of weeks. He said the US team will be led by the current US Special Representative for North Korea, Stephen Biegun.

Trump invited Kim to the White House. He later acknowledged such a visit would likely not come soon.

Yes, the meeting came after Trump tweeted Kim an invitation

The meeting happened hours after Trump extended what he claimed was a spontaneous invitation on Twitter to Kim to shake hands at the DMZ.

In a Saturday morning tweet from his hotel in Japan, Trump said if Kim was interested he'd be open to a greeting on the border.

"If Chairman Kim of North Korea sees this, I would meet him at the Border/DMZ just to shake his hand and say Hello(?)!" Trump wrote.

Biegun held secret discussions Saturday night at the DMZ to set up the meeting between the two leaders, a US senior official told CNN.

Kim confirmed that he heard from Trump Saturday afternoon and wanted to meet him again. "I believe that meeting here, which is a symbol of division and a hostile past, I think meeting here, two countries that have a hostile past, we are showcasing to the world that we have a new present and we have a positive meeting going forward," Kim said. "Some are saying this meeting was pre-planned but I was very surprised to hear about your offer on the tweet."

2020 Democrats were not happy about the 'photo op'

Reaction quickly poured in from Democrats running for president in 2020 , with many skeptical any tangible results or progress would be made as a result of the meeting.

Sen. Elizabeth Warren of Massachusetts said Trump shouldn't be "squandering American influence on photo ops and exchanging love letters with a ruthless dictator," in a post on Twitter.

Sen. Amy Klobuchar of Minnesota said achieving denuclearization is "not as easy as just going and, you know, bringing a hot dish over the fence to the dictator next door," on CNN's "State of the Union" on Sunday.

While Sen. Bernie Sanders of Vermont said he had "no problem" with Trump meeting with Kim, he took issue with Trump's "incredible inconsistencies."

"I don't want it simply to be a photo opportunity," Sanders told ABC.

A spokesman for Joe Biden, Andrew Bates, said Trump "fawned over Kim Jong -un -- to whom he's made numerous concessions for negligible gain."

And Sen. Kamala Harris tweeted, "This President should take the North Korean nuclear threat and its crimes against humanity seriously. This is not a photo-op. Our security and our values are at stake."

But the Pope praised the meeting

Pope Francis on Sunday commended the meeting between the two leaders, saying, "In the last hours, we have assisted in Korea a good example of a culture of dialogue."

During his remarks, which came after his weekly Sunday prayer held in St Peter's Square in Rome, the Pope said the meeting "constitutes a step further in the walk of peace. Not only on that peninsula but in the entire world."

And the White House press secretary got in 'an all out brawl'

Stephanie Grisham, the new White House press secretary, was bruised during a scuffle with North Korean officials outside of the room where the two leaders met on Sunday.

A source at the scene said Grisham got in "an all out brawl" with North Korean officials as American and North Korean reporters were hustled in to view the summit. Grisham was bruised a bit in the scuffle, the source added.