In what unexpected way were Post-it Notes invented at 3M in the 1970s?

Some of the world's most successful products were created by accident or as solutions to entirely different problems. The journey from laboratory experiment to retail phenomenon often involves unexpected twists and surprising discoveries. This poll explores the fascinating origin story behind one of the most ubiquitous office supplies that revolutionized how we organize information and communicate quick messages in both professional and personal settings.

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As a failed adhesive that was too weak but perfectly removable, initially considered a manufacturing mistake
As a deliberate attempt to create bookmarks for hymnals that wouldn't damage the pages
As a heat-resistant alternative to tape for NASA's space program that was rejected for being too flimsy
As a solution for hospital patient charts that needed to be updated frequently without rewriting entire documents