Computing devices, computer-readable media storing computer-executable instructions, methods, and systems for discovering, organizing, and presenting supplemental content are disclosed. A discovery system may be used to discover an item, such as a supplemental content presentation application, which, when launched may present supplemental content to a user while the user is consuming primary content. The supplemental content presentation application may also present a timeline that users may interact with to view different portions of the supplemental content. The timeline may also be modified by adding markers along the timeline so that when a marker is selected, a particular piece of supplemental content is presented.