This is absolutely historic. Never before have the leaders of these two countries met. These are countries that are still technically at war. However, it may be historic that they are meeting, but no one should think that this is a deal.
US President Donald Trump and South Korean leader Kim Jong-un signed an agreement on Tuesday but this is likely going to be a long and bumpy road ahead.
The other main observation is how fast this has moved.
If you think of that period of last summer, it was probably the tensest period in the relationship between North and South Korea over the last 70 years.
We sort of know what then happened.
Al Jazeera learned that the day after Trump spoke at the General Assembly in September, the North Korean foreign minister met Antonio Guterres, the UN secretary-general, saying the UN could send a senior UN official to Pyongyang.
Weeks later Jeffrey Feldman, the then-political affairs chief of the UN went to North Korea, where he said that Kim made an overture, suggesting that he should offer an olive branch by sending a delegation to the Olympics in South Korea.
This move opened up diplomacy between South Korea and North Korea.
The South Koreans got the CIA involved and they led the US initiative, leading to the secret meeting between Pompeo and Kim in Pyongyang at Easter, where it was revealed that diplomacy had reached a different pace.
Pompeo returned to Pyongyang, on-off contacts continued, which have led to this historic summit today.
This was probably the biggest day of diplomacy in the last decade, apart from one other day, when the JCPOA, or Iran deal, was finally signed in Vienna in July 2015.
And that was the deal that Trump has pulled out of, setting himself an extremely high bar for the Korean diplomatic process.
Trump needed to find something better than the Iran deal. All of this makes it fascinating, interesting, historic, but very much in its early stages.