Explore the intricate world of retroviruses in this comprehensive lecture from the Prospects in Theoretical Physics 2019 series. Delve into the retrovirus life cycle, examining late steps, integration processes, and germline tumors. Investigate the structure and function of retroviral particles, receptors, and envelopes. Gain insights into reverse transcription, focusing on reverse transcriptase enzymes, particularly HIV reverse transcriptase, and DNA synthesis mechanisms. Analyze integrase binding sites and their role in viral replication. Understand the evolutionary consequences of retroviruses on their hosts, bridging the gap between biology and physics in this in-depth presentation by Steve Goff.