Natalie asked about antimatter, which is made of antiparticles. All the stuff you know (matter) is made of particles like protons, neutrons, and electrons. (You might need a refresher, so let Professor Venus Flytrap take care of that if you get a chance.) (The Clear Science staff love that guy.)
Turns out all these particle have opposites, and those are antiparticles. You know a proton is positive, but an antiproton is negative. The opposite of an electron is a positron. These particles are real, and can be observed in high-energy physics experiments, like with a particle accelerator.
Particle and antiparticles will annihilate if they collide. Note that that happens not just because of the opposite charge: neutrons and antineutrons are both non-charged, but they still annihilate if they come together. (They’re made of quarks and antiquarks, and those annihilate when joined.)
