Everything that you can see and touch in the Universe is made of atoms, which are themselves made of protons, neutrons, and electrons. But did you know that every type of particle has a twin, called its antiparticle? Looking at an antiparticle is a bit like looking at a particle in the mirror: most of its properties, like mass, are the same, but some are flipped, like electric charge. We can imagine worlds that are made up entirely of antimatter rather than matter, and an alien living in that mirror world would mostly see it the same way we see our own. But why, then, do we see matter when we look around and not antimatter? This is a mystery that physicists are still working to solve. In this talk, we will journey through the looking glass into the realm of antimatter, looking at the Universe from both sides of the mirror. In doing so, we may come to a better understanding of ourselves and our place in the world.