Kim Jong-un has become the first North Korean leader to set foot in South Korea by crossing the military line that has divided the peninsula since the end of the Korean War in 1953.
In a moment rich with symbolism and pomp, South Korean leader Moon Jae-in and Mr Kim shook hands at the border.
Mr Kim said he hoped for “frank” discussion in a warm opening exchange.
Just months ago North Korean rhetoric was warlike, but now they may discuss a peace treaty and nuclear weapons.
Much of what the summit will focus on has been agreed in advance, but many analysts remain deeply sceptical about the North’s apparent enthusiasm for engagement.
Then audiences watched in surprise as Mr Kim invited the South Korean president to step briefly across the demarcation line into North Korea, before the pair stepped back into South Korea – all the while holding hands.
It was an apparently unscripted moment during a highly choreographed sequence of events.
The first session has broken up and the pair will have lunch separately. Mr Kim returned to the North in a heavily guarded black limousine for lunch. He will cross back over the border in the afternoon to resume discussions.