Here's a wonderful video on the Veritasium YouTube channel of how the blue LED was invented and also an excellent explanation of band gaps:
https://www.youtube.com/watch?v=AF8d72mA41M&ab_channel=Veritasium
A nice introduction to the history of electron microscopes:
https://www.youtube.com/watch?v=88bMVbx1dzM
Which answers the question: "What if you just keep zooming in?"