"Sometimes it gets pretty serious," said Riley Forrestal, a competitor from Maryland.
It is called pin trading. More than 8,000 kids from all over the world bring badges that represent their home country.
"There's some people that come here every year just to trade," said James Watkins, a competitor from Maryland. "They have beach towels full of pins."
James Watkins has been trading and collecting for years.
"I have a lot of these," said Watkins. "I have one from China. I have one from Kentucky. I have one from Nebraska and I have a couple from Colorado."
He said he is proud of his collection, especially a rare pink crab pin.
"I'm not trading it," said Watkins. "It's a very rare pin and there's only like 100 of them."
There's rules when you pin trade and it takes a little bit of bargaining.
"All the pin trading is supposed to be fair, so you're not supposed to trade like a very small pin for a large one and you're not supposed to trick people," said Watkins.
"You have to know which pin is equal to what you're about to give," said Forrestal.
Some of them will search for the pin they need all week long and they said it's worth it.
"I feel just complete, "said Catherine Souter, a competitor from Maryland.
They take little pieces of the world with them.
"I probably will remember this and it will show that DI is widespread -- not just in America and Maryland," said Watkins.