The "Crash Course" YouTube channel was conceived by the Green Brothers after YouTube approached them with an opportunity to launch one of the initial YouTube-funded channels as part of the platform's original channel initiative. The channel was teased in December 2011, and then launched on January 26, 2012, with the first episode of its "World History" series, hosted by John Green. The episode covered the Agricultural Revolution, and a new episode aired on YouTube every Thursday through November 9, 2012. Hank Green's first series, "Crash Course Biology", then launched on January 30, 2012, with its first episode covering carbon. A new episode aired on YouTube every Monday until October 22 of that year. The brothers would then go on to end 2012 with two shorter series, with John and Hank teaching English literature and ecology, respectively.