Lightbulb

A favorite Thomas Edison quote of mine is: “Just because something doesn’t do what you planned it to do doesn’t mean it’s useless.”
Off the top of my head, I can think of two instances where the disappointing result turned into very successful products.
The most recent was the invention of the adhesive that makes low-tack items like PostIt notes possible. The discoverer failed to create what he intended but found use in another application.
A second instance appears to have been the crackle glaze on Ming dynasty vases. It may have been an accidental discovery. But, as a wag once joked, “it’s a mistake, but what a mistake!” This last may be apocryphal.
It’s easy to dismiss what doesn’t appear to be of immediate use.
The idea of sowing crops instead of just gathering what was available; domestic animals; or pets like dogs and cats. None may have begun as ideas that set off cries of “let’s do it now!”
OK, it wouldn’t have been a “lightbulb” idea for the Stone Age – more like a torch?