For example, there are four fundamental forces and a table of fundamental particles. Why? Don't know, we just noticed them.
All of chemistry seems to be determined by properties and interactions of electrons, which also determines biology. Where do these electrons come from? Don't know, just there.
The gravitational constant pops up in bunch of equations. So does the speed of light. Why do they have their specific values? Why is there even a speed limit in the universe (which expanding space violates)? Don't know, we just noticed it.