Specifically, he is famous for:

* The theory of relativity: This theory revolutionized our understanding of gravity, space, and time. It includes both the special theory of relativity (dealing with objects moving at high speeds) and the general theory of relativity (dealing with gravity as a curvature of spacetime).

* The photoelectric effect: This explained the phenomenon of light ejecting electrons from metals and earned him the Nobel Prize in Physics in 1921.

* Mass-energy equivalence: His famous equation E=mc² describes the relationship between energy and mass, which has profound implications for nuclear physics and cosmology.

While Einstein also made significant contributions to other areas of physics, these three are the most recognized and groundbreaking achievements that have shaped our understanding of the universe.