Matter and anti-matter are simply some infantile thinkings that scientists will grow out of if people happen to last for another 500 years.
Are you joking? We have antimatter. We have been able to make it and collect it, in actual physical form.
Not joking. Science has been aware of parallel universes for years - http://manyuniverses.com/. The material of parallel universes exists in the empty spaces between the protons and electrons of our atoms, as well as any other empty space in our universe. The reason that we don't observe or feel the parallel universes is that they are "out of phase" dimensionally, with our universe. Yet there are places where we almost become "in phase" with some of these universes. The points of in-phase are the areas where two or more of the other universes touch, thereby actually creating the subatomic particles of our universe. And when ours touches andother, we create some subatomic particles of some other universe.
Now, what does this have to do with matter and antimatter? It all lies in the facts of vibrations in the ether. The whole mega-universe is an elastic solid - the ether - made up of all the parallel universes acting in conjunction with all the others, controlled according to dimensional laws. The materials of all the universes are simply vibrations - http://www.pbs.org/wgbh/nova/blogs/physics/2013/08/the-good-vibrations-of-quantum-field-theories/. They are vibrations that come together in ways that give us a thing that we call matter. What scientists have known for years is that antimatter is simply other vibrations that act somewhat opposite from our matter vibrations. There may be many different forms of matter and antimatter throughout the parallel universes.
To say it straight forward, there isn't any matter, or antimatter for that matter (pun intended). It's all vibrations in the ether. There is neither substance nor size to the vibrations. There is simply vibrations.
Absolutely important entropy.