For most kinds of particles there is postulated to exist a corresponding antiparticle, which is of the same mass but an opposite charge. These antiparticles have only recently been observed in laboratory settings for the first time, and they are very difficult to isolate and study experimentally. This is because particle and antiparticle pairs collide to generate photons of light in a process that annihilates the particle and antiparticle pair. Antiparticles are not well understood and are an active area of research related to nuclear chemistry. Antimatter is just matter made up of antiparticles, in the same way that normal matter is made up of particles. There has been postulated to be an equal amount of matter and antimatter in the universe, though the observations made to date do not suggest this to be the case. This represents an unresolved dilemma that scientists hope to someday better understand. These types of fundamental, unresolved problems are a big part of the reason science is so interesting!