Abstract: Dark matter is believed to comprise five-sixths of the matter in the universe, and is one of the strongest pieces of evidence for new fundamental physics. But dark matter does not interact directly with light, making it very difficult to detect except by its gravity. I will describe how dark matter collisions might produce high-energy particles observable by Earth-based telescopes, and how we can attempt to tease out those signals from the background. In the last few years, such attempts have unveiled fascinating new structures in high-energy gamma rays: understanding these observations may either reveal the new physics of dark matter, or probe the deep history of our Milky Way Galaxy.