There are a large number of sub-branches of physics, but examples include astrophysics, biophysics, electronics, high energy physics and molecular physics. Most scientists become experts in one particular branch, as there is too much knowledge and information in physics as a whole for one person to study it all.
Particle physics is the study of the very small particles that make up atoms. This branch of physics is closely linked with high energy physics, as small particles can often only be studied by colliding particles at high velocities.
Relativity is a branch of physics that was originally developed by Albert Einstein. In this branch, high speed objects are studied to determine how the universe behaves when moving near the speed of light.
There are a number of branches that are exclusively about studying space. Astronomy, for example, is the general study of the universe and the objects within it. Astrophysics is closely related, but is the study of how the physical properties of materials vary throughout the universe.
Cosmology focuses on how the universe began, and how it has changed as a whole. There are a variety of other branches of physics. Examples include computational physics, fluid dynamics and atomic physics.