While he is most famous for his theory of relativity, his studies and contributions spanned several areas of physics including:

* General Relativity: This theory revolutionized our understanding of gravity and the universe.

* Special Relativity: This theory explained the relationship between space and time and how they are affected by motion.

* Quantum Mechanics: He made significant contributions to this field, though he was somewhat skeptical of some of its interpretations.

* Statistical Mechanics: He applied statistical methods to understand the behavior of large collections of particles.

* Cosmology: His work on general relativity led to his theories about the expansion of the universe and the structure of the cosmos.

Essentially, Albert Einstein was a pioneer in nearly every field of physics in the early 20th century, leaving an enduring legacy on modern science.