The Post-it Note sat in a drawer for six years before anyone used it

Spencer Silver invented a weak, repositionable adhesive at 3M in 1968 while trying to make a super-strong glue. He promoted it internally for years but couldn't find an application. In 1974, colleague Art Fry remembered Silver's adhesive while frustrated that his hymn-book bookmarks kept falling out. He used the adhesive to make a sticky but removable bookmark — and the Post-it Note was born. 3M launched it nationally in 1980; within a year it was one of the company's top five selling products. The story is the canonical example of a solution waiting for its problem.

Source: Nayak & Ketteringham, Breakthroughs! (1986)