After eight months of investigation, InsideClimate News presents this multi-part history of Exxon's engagement with the emerging science of climate change. The story spans four decades, and is based on primary sources including internal company files dating back to the late 1970s, interviews with former company employees, and other evidence, much of which is being published here for the first time. It describes how Exxon conducted cutting-edge climate research decades ago and then, without revealing all that it had learned, worked at the forefront of climate denial, manufacturing doubt about the scientific consensus that its own scientists had confirmed.