Plasma is one of four states of matter. You’re probably pretty familiar with the other three: solids, liquids and gases. Although it is the least familiar state of matter to us here on Earth, plasma is actually the most common form of matter – in fact, plasma makes up 99% of all visible matter in the Universe. Matter Sorter Drop each object into a 'states of matter' bin. You don’t see lots of plasmas here on Earth because it’s too cold for most matter to reach that state. In the rest of the Universe however, plasma is more common than solids, liquids or gases. Our Sun is made of plasma, as are all stars. Their intense heat can turn nearby gas to plasma. Although naturally occurring plasma is rare on Earth (e.g. a lightning strike), there are many man-made examples. Plasma glows when it conducts electricity in neon signs and fluorescent bulbs. The hottest candle flame is plasma. Scientists have constructed special chambers to experiment with plasma in laboratories. Plasmas come in many varieties depending on their temperature and density. There are often so few plasma particles (ions and electrons) in a volume of space (thus the number density, particles per unit volume, is low) that a spacecraft could fly right through them without damage – even though the temperature of the plasma is thousands of degrees. However, really high energy charged particles can damage spacecraft. The graphic above (temperature vs. number density) shows some of the many forms a plasma can take (both natural and manmade).