There are lots of important moments I guess, I would credit the main break in practicality to the ~1990 Swiss/German stuff: https://people.idsia.ch/~juergen/dee

There are lots of important moments I guess, I would credit the main break in practicality to the ~1990 Swiss/German stuff: https://people.idsia.ch/~juergen/deep-learning-miraculous-year-1990-1991.html#Sec.%201 https://people.idsia.ch/~juergen/deep-learning-miraculous-ye... But still even the early perceptrons stuff was applied research, I wouldn't call it purely theoretical by any means.