The useful little Post-It is 25 this year.
"...the Post-it Note was more than just a practical tool-it was also a psychological one. Compared to the clunky machines of the 1980s that generated all those documents, it was a vision of high-tech minimalism. Its edges were sharp and square, with no ugly binding, no perforations, no metal rings. Its color, a subtle but attention-getting yellow, was somehow like the color of thought itself, a lightbulb going off in your head. Devoid of any other graphic elements, it had the effect of a clean, calming, blank screen. And, yet, for all its streamlined efficiency, it was playful and user-friendly..."
"Perhaps because these funny little yellow notes that didn’t stick so well have managed to stick around for a quarter of a century, many of the best-known Post-it Note anecdotes document their surprising bonding power. For example, there’s the one about the Post-it Note in Charleston, South Carolina, that survived Hurricane Hugo. While homeowner Bruce Brakefield lost eight oak trees in his front yard to the 140 mph winds, the note on his front door-it read “Baby Sleeping”-withstood the storm. Another Post-it Note endured a cross-country trip on the side of a moving van.
Ultimately, it’s not their bonding power that makes them so culturally resonant. Instead, it’s their flexibility, their impermanence, their ability to attach themselves to something, then detach themselves from it, then start the process all over again."
Here's the story of the Post-It and its inventor.