1. Theory of Relativity: This is his most famous contribution, encompassing both special relativity (dealing with constant motion) and general relativity (dealing with gravity and acceleration).

2. Mass-Energy Equivalence (E=mc²): This equation, derived from special relativity, shows the relationship between mass and energy, explaining how matter can be converted into energy and vice versa.

3. Photoelectric Effect: Einstein explained this phenomenon, in which light can knock electrons off of metal surfaces, by proposing that light exists as packets of energy called photons. This work earned him the Nobel Prize in Physics in 1921.

4. Brownian Motion: Einstein provided a mathematical explanation for this random movement of particles suspended in a fluid, further solidifying the atomic theory of matter.

5. Contributions to Quantum Mechanics: While not solely responsible for its development, Einstein made significant contributions to the theory of quantum mechanics, which describes the behavior of matter at the atomic and subatomic level.

6. Thought Experiments: Einstein was famous for using thought experiments to explore complex scientific concepts, such as the famous "twin paradox" in special relativity.

7. Pacifism and Humanitarianism: Einstein was a strong advocate for peace and social justice, and he spoke out against war and nuclear weapons.

8. Intellectual Icon: Einstein's genius and unconventional personality made him a global icon, and his image continues to be a symbol of intelligence and scientific achievement.

His work revolutionized our understanding of space, time, gravity, and the very nature of light. Einstein's contributions continue to be fundamental to modern physics and have had a profound impact on our understanding of the universe.