I remember first learning about chirality in my biochemistry course in college, and it was definitely a mind-blower. I had already started to understand that molecules had 3d structures, but the idea (and attempting to visualize it mentally) of mirror image molecules stretched my brain significantly.

It's also still amazing to me how people first recognized this: poking around looking at the crystals that form in the bottom of a wine under a microscope, noticing that some of them were mirror images of the other, and then seperating them manually with tweezer, dissolving them into two different solutions, and demonstrating that they rotated light in opposite directions.