Post-It Notes were originally yellow pieces of paper with a sticky edge used for stick-on messages in offices and homes everywhere.

Post-Its were the inspiration of Arthur Fry, a chemist at the Minnesota Mining and Manufacturing Company (3M). One Sunday in 1974 at the North Presbyterian Church, Fry began considering better ways to mark his place in his hymnal; the slips of paper he used kept falling out, and he could not find the right hymn when it came time to sing. Suddenly he thought of a failed experiment of a 3M colleague, Spencer Silver. Trying to develop a super-strong adhesive, Silver had produced a super-weak one instead--just the thing for his purposes, Fry reasoned.

Fry experimented with the glue, adjusting the formula so the notes would not leave a residue when peeled off, and passed out samples to coworkers until he convinced 3M management to promote the product as notepaper. "Press & Peel" was test-marketed in 1977. The notes did not become popular until 3M promoted their use by distributing free samples. A flood of samples and advertising in Boise, Idaho, in 1978 produced heavy sales, and national marketing began in 1979.

Today, Post-It Notes come in a variety of colors and sizes, are a best-seller for 3M, and seem indispensable to legions of devoted users.