Running Apple 1 software on a breadboard computer (Wozmon) [video]
It's been said many times here before, but Woz's "annus mirabilis" from March 1975 to April 1977 when at just 26yo, he  designed, implemented and launched the hardware, kernel, sound and color output as well as a BASIC interpreter (and much more) for the Apple I and II is one of history's greatest technological achievements. It was a tour de force of talent which is astounding to this day.And Ben Eater has taught me more about how computer hardware and software work at the lowest level than any other resource I've come across in my 25 years in the tech industry. Truly inspiring.