when were post it notes invented

Post-it Notes were invented in 1968 by Spencer Silver, a scientist at 3M, who accidentally created a low-tack, reusable adhesive while trying to develop a super-strong one. The idea to use this adhesive for sticky notes came later in 1974 when Art Fry, another 3M employee, used it to anchor bookmarks in his hymn book. After initial challenges, the product was successfully launched across the United States in April 1980 under the name "Post-it Note".