The protons and neutrons that make up atoms are made of even smaller things called quarks (which are "glued" together by things called "gluons"). At incredibly high temperatures over 2 trillion Kelvin, quarks and gluons turn into another state of matter. Humans can make a little bit of quark-gluon plasma in the Large Hadron Collider at CERN, but it doesn't last long before cooling down.