Neutronium

Neutronium is like a bunch of tiny balls called neutrons, all squished together super tight. It's kind of like when you're playing with clay and you squish it really hard so it all sticks together.

These neutrons are like the building blocks of atoms, which make up everything around us. But when they're packed together so tightly, they become a completely different thing altogether.

Sometimes, really big stars that have run out of fuel explode in a big boom called a supernova. When this happens, lots of the neutrons from these stars get squished together and become neutronium.

Because it's so squished together, neutronium is really heavy, much heavier than any other material we know of. And because it's so dense, you can't really touch it or break it apart - it's just too strong!

Scientists are still learning a lot about neutronium and how it behaves, but it's pretty cool to think about all those tiny neutrons sticking together so tightly!