It's taken billions of pounds and lots of attempts, but scientists say they've recreated the start of the Universe.
Some people think the universe was formed by tiny particles smashing into each other and joining to make planets - known as the Big Bang theory.
To test the idea, scientists have been firing beams of particles into each other to create a mini-Big Bang and see what happens.
The explosion it created was one million times hotter than the Sun!
Apparently that's 10 trillion degrees C!
Part of the Large Hadron Collider (LHC)
The huge machine at the heart of the massive experiment is the Large Hadron Collider (LHC) - aka The Smasher!
It's the largest and most complicated scientific instrument in the world, cost billions of pounds to build, and is kept in a 16-mile circular tunnel under the French-Swiss border near Geneva.
The LHC is something called a particle accelerator, which means it can fire the tiny particles at super-fast speeds so they smash into each other head-on at super-fast speeds to create the explosions that recreate the mini-Big Bang.
It's had loads of problems since it was first switched on in 2008.
But now scientists have created their first mini-Big Bang, they're hoping to learn more about what the Universe was made of immediately after it was created.