Special Relativity
When you go really really fast, things get weird.
General Relativity
When you look at stuff that's really really big, things get weird.
Quantum Mechanics
When you look at stuff that's really really small, things get weird.
String Theory or Superstring Theory or M-Theory
Even though the above types of weirdness seem completely different and unrelated, they're really all the same weirdness if you squint just right.