Explore the groundbreaking discoveries and insights gained from 15 years of cosmic observation with the Fermi Gamma-ray Space Telescope's Large Area Telescope (LAT) in this captivating physics colloquium. Delve into the fascinating world of high-energy astrophysics, learning about pulsars, neutron stars, supernova remnants, cosmic rays, binary systems, active galactic nuclei, and gamma-ray bursts. Gain an understanding of how international collaboration has been crucial to Fermi's scientific success and the challenges overcome in such partnerships. Discover the telescope's potential contributions to the emerging field of time-domain and multi-messenger observations, offering a glimpse into the future of astrophysical research and our understanding of the vibrant universe.