Post-it began as a weak glue nobody at 3M could find a use for.
In 1968, scientist Spencer Silver created an adhesive that stuck lightly and peeled off too easily. For years, that looked like the problem. Then Art Fry used it to hold bookmarks in a hymnal that kept sliding out. The glue too weak to bond was perfect for a note you peel off and move.
Post-it on Brandseum