SceneSnaps on Instagram: "The Big Bang Theory – Plot & Overview The Big Bang Theory is a popular American sitcom that aired from 2007 to 2019. The show centers on a group of highly intelligent but socially awkward friends—mainly scientists—whose lives change when they interact with people outside their academic world. Plot Overview: The story primarily follows Leonard Hofstadter and Sheldon Cooper, two brilliant physicists who share an apartment. Their structured, science-driven lives are turned