A flexagon is a polygon folded from a strip of paper, which has the fascinating property of changing faces when it is flexed.

Flexagons where discovered by accident in 1939, when Arthur Stone, a 23 year old graduate student at Princeton, had to trim off a strip of paper from his British notebook page to be able to fit it into his American binder. By folding the trimmed-off strip of paper in various ways, he soon constructed the first flexagon: the three-faced trihexaflexagon.

I will elaborate on some interesting aspects of the history and properties of flexagons. I will also show you how to construct and flex your own trihexaflexagon, which you may take with you to dazzle your family members and friends. We will also use the trihexaflexagon to sneak up on a group.