Taking which online or offline courses have humbled you?

Question

By humbling I don't mean in a negative way; rather in a way that made you really appreciate the subject by giving you a new mental model by rewiring your brain.For me:Programming Languages A, B and C by Prof Dan Grossman on Coursera.It taught me the inter relations between different programming paradigms and how to pick up new programming languages. More clearly what to look for in the documentation to form a working mental model of a new programming language.

mindcrime · Accepted Answer

I'm not sure if "humbled" is the right word or not, but Calculus II had a somewhat profound effect on me. I think it was studying Calc II that I first started to feel like I could finally start to see at the least the shadows of the inherent appeal of math. I also felt like Calc II was a big step towards understanding the level of math that starts to have real world applications outside of contrived / toy examples that you find in textbooks.