The dawning of the quantum age.
It was only a few years ago that we were confidently assured quantum computing was โimpossible.โ And hilariously, that was after there were already working (but rudimentary!) quantum computers.
Some things are indeed impossible but others are โimpossible.โ But in general, people have a really bad idea of what that is. (Space travel is another example of the โimpossibleโ rather than the actually impossible.)