I'd structure it historically. Newton most elegantly developed the idea of inertial frames of reference (along with the math to work out extraordinary solutions) in his work Principia Mathematica. Originally iirc (not a physics major, so someone step in and correcr me if I err) this was defined as a system at rest or constant velocity, but extended to include parallel and uniformly accelerating systems in corollary 6). All was well for bout 200 years until Einstein wondered about such in the context of near light speeds. The story has it that at 16 (about your age) he was wondering about such, and then after an undistinguished academic career that earned a PhD but no post-doc position on acct of his mentor' unflattering letter of (non)recommendation, set about in earnest as a patent clerk to finish the problem. This was SR, which in itself was an extraordinary work, but likely would have been developed within a decade or two by someone else that extends the notion of reference frame to relativistic velocities. The real mind blowing stuff was of course, GR. That along with Principia, and Darwins Origin of Species, are my pick (and likely most peoples) as the top three scientific achievements of all time.