What was the failed adhesive experiment at 3M that eventually led to the invention of Post-it Notes?

The world of consumer products is full of accidental inventions that changed how we work and live. Some of the most ubiquitous products we use daily were discovered through fortunate laboratory mistakes or persistent innovation against the odds. This poll tests your knowledge about one such revolutionary office product that transformed how we organize information and communicate in workplaces worldwide.

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An attempt to create a super-strong adhesive that accidentally produced a weak, removable one
A waterproof paper experiment that unexpectedly created paper with adhesive properties
A transparent tape upgrade that resulted in colored, non-transparent sticky paper
An experiment to create heat-resistant labels that instead produced temperature-sensitive sticky notes