Plasma is the fourth state of matter, alongside solid, liquid, and gas. When you heat a gas to extremely high temperatures (thousands of degrees), its atoms break apart into electrically charged particles, creating plasma. The sun is a giant ball of plasma, and lightning bolts are plasma streaking through the air.

Plasma might sound exotic, but you've probably seen it many times. Neon signs glow with plasma inside their tubes. Fluorescent lights in classrooms work the same way. When you flip the switch, electricity energizes the gas inside, turning it into glowing plasma. Even the screens of some older televisions used tiny pockets of plasma to create their picture.

Scientists study plasma to understand stars and develop new technologies. They're working on fusion reactors that could someday generate enormous amounts of clean energy by containing super-hot plasma, mimicking what happens inside the sun.

The word plasma also means something completely different in biology: the yellowish liquid part of blood that carries red cells, white cells, and nutrients throughout your body. When doctors talk about donating plasma, they mean this liquid portion of blood, not the superhot state of matter.