We know that when an electron, which is a particle of matter, and a positron, which is a particle of antimatter, collide, they destroy each other because the energy in the two particles is carried away by two real photons. When all matter destroys an equal amount of antimatter, the same thing happens.
Positron annihilation is used in many imaging systems, such as gamma cameras, SPECT, PET, CT-PET, etc. One of the most active areas of research in materials science was the study of semiconductors, which came after the first studies of metals and alloys.