People shake hands all the time. To say hello, to make friends, to say well done... There's loads of reasons.
In fact, there's even a guide to why we shake hands right here.
But some handshakes mean more than others.
On Tuesday, North Korea's leader Kim Jong-un and US President Donald Trump made history when they met in Singapore.
The world was watching as the two man shook hands.
The moment is so significant as no serving US president has ever met with the country's leader.
The meeting between them is to discuss how the countries can end the arguments they have had about North Korea's nuclear weapons.
But this wasn't the only of Kim Jong-un's handshakes that has recently made history.
At the end of April, he shook hands with another man in a move that was called one of the most important handshakes in over 50 years.
North Korea's Kim Jong-un and South Korea's Moon Jae-in shook hands at the border between the two countries, before symbolically stepping back-and-forth across the border.
Since the Korean war ended in 1953, North and South Korea have been enemies. But after this meeting the two leaders agreed to turn their border into a 'peace zone'.
Shaking hands always makes a good photograph and when people who've been rivals or enemies do it, it can make big news all around the world.
Nelson Mandela and François Pienaar
Here's South Africa's President Nelson Mandela congratulating South Africa's rugby team captain François Pienaar, after his team's victory in the World Cup final back in 1995.
At the time South Africa was a deeply divided country, It had only just ended apartheid - a racist system where white and black people in the country lived separate lives.
Nelson Mandela had just been elected president - the first black person have the job - and he wanted to bring people of different races together in South Africa.
Rugby in South Africa was a sport heavily linked to the white apartheid rulers.
However, the World Cup slogan had been "one team, one country," with the organisers hoping the event would bring the country together behind the national team.
Mandela gave his support to the South African team, which helped to unite the country. Nothing symbolised Mandela's hope for the new South Africa like him shaking hands with the country's rugby captain.
Jose Mourinho and Pep Guardiola
They'd shaken hands many times before but for some reason everyone was waiting to see if Pep Guardiola and Jose Mourinho would shake hands after they had become managers of Manchester City and Manchester United.
When they'd been rival managers in Spain (Pep at Barcelona and Jose at Real Madrid), there had been some nasty arguments between them and they'd been really unfriendly towards each other.
They then worked in different countries for a few years, but now they were back as rivals and everyone was wondering, would they or wouldn't they shake hands?
What happened? They shook hands, of course - it's only football!
Jose Mourinho said he didn't understand why people were even asking the question and Pep Guardiola said they were both "polite guys" who simply "want to win".
Selena Gomez and Francia Raisa
It's more of a hand-hold than a hand-shake, but this perfectly sums up the incredible friendship of Selena Gomez and her friend Francia Raisa, who donated an organ to her.
As the two recovered side-by-side in their hospital beds, Selena said: "She gave me the ultimate gift and sacrifice by donating her kidney to me. I am incredibly blessed. I love you so much sis."
Meanwhile Francia said: "I am beyond grateful that God would trust me with something that not only saved a life, but changed mine in the process."
The iconic picture came after Selena had cancelled her world tour, and helped to raise awareness of her condition - Lupus.
Donald Trump and Poland's First Lady
Donald Trump had only been president for a few months when he was joined by his wife on a visit to Poland.
The meeting began with the traditional welcome, but it went viral when there was an entirely accidental handshake calamity.
Poland's first lady Agata Kornhauser-Duda went to shake Melania's hand just as Donald went to shake her hand... and, well, the internet went crazy.
It was just a little bit embarrassing for both of them - especially with the world's media there to see it happen!
It's all ok though, we're told they did shake hands properly later on. But by then all cameras weren't around...