Mathematical challenges take undergrad in a new direction
spectrum.mit.edu
spectrum.mit.edu
Like, the E8 Lie Group probably contains the secret to manmade wormholes, faster-than-light travel, and manipulating higher dimensional space, but we won't know it for hundreds of years. (or at least until we invent AGI). Something like that.
But I did enter school interested in biomedical engineering--in part because my parents were both in life sciences in various ways. And I probably liked chemistry more than physics in high school. That more or less lasted through taking organic chemistry which I did not... umm, connect with.