* The Theory of Relativity: This includes both special relativity (dealing with the relationship between space and time) and general relativity (describing gravity as a curvature of spacetime).
* The Photoelectric Effect: This explained how light can knock electrons off a metal surface, earning him the Nobel Prize in Physics in 1921.
* Brownian Motion: This explained the random movement of particles suspended in a fluid, providing strong evidence for the existence of atoms.
While his primary focus was on physics, he also explored and made contributions to other fields, including mathematics, philosophy, and cosmology.
