In 2010, Mayank Sharma of New Delhi, India contracted tubercular meningitis, a serious inflammation of the central nervous system. After a week in the hospital, he emerged without any memory of ever getting sick or of the first twenty-seven years of his life. He began messaging the people who came up in Facebook’s People You May Know feature to start piecing his life back together.

After freshman goalie Daniel Cui became the scapegoat for a losing season, the whole high school rallied to defend him. More than 100 students changed their profile pictures to a photo of Cui making a save, and with newfound confidence, Cui returned the next season to play the game of his life and lead his team to a win.

In January 2011, Oregon State University ichthyologist Brian Sidlauskas led a research expedition into the little-known Cuyuni River region of Guyana in South America. His team documented more than 5,000 fish, but Guyana's immigration policies required them to identify and catalog every specimen they wanted to bring back—a nearly impossible task, especially on a tight schedule. Sidlauskas uploaded his research photos to Facebook and tagged members of the scientific community who were able to identify almost all of the photos in under 24 hours.

Exploring the history and science behind the "six degrees of separation" theory. Who came up with the idea? Is six even the right number? Facebook's Nicholas Arioli explores the history of Six Degrees of Separation in our first Facebook Stories audio Podcast.