On April 6, 1980, 3M begins sales of Post-it Notes. The canary yellow sticky pads quickly become one of the best-selling office supply products in history and a ubiquitous staple in schools and offices around the world. No, Post-it Notes were not invented by the title characters in Romy and Michele’s High School Reunion, but by 3M scientists Spencer Silver and Arthur Fry. In 1968, Silver was working as a 3M research chemist when he developed an unusual adhesive made of tiny acrylic spheres—sticky enough to hold papers together, but weak enough to peel away cleanly and be reused. Because the microspheres touched surfaces at only a few points, the adhesive retained its tack even after repeated use. For years, 3M struggled to find a practical consumer use. A prototype bulletin board coated with the adhesive failed when dust and dirt reduced its sticking power. Silver’s creation remained a solution in search of a problem—until Fry, a 3M product development specialist, found one.…