Which scientific innovation was NOT initially developed for commercial use, but was accidentally discovered during a failed experiment for another product?

The intersection of scientific research and product development has led to some of the most innovative consumer products in history. Many everyday items we now take for granted were once revolutionary scientific breakthroughs. Test your knowledge about the science behind famous product innovations and how laboratory discoveries transformed into commercial success stories.

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Graphene (ultra-thin carbon material)
Super Glue (cyanoacrylate adhesive)
OLED display technology
mRNA vaccine delivery system