Modern physics is an effort to understand the underlying processes of the interactions with matter, utilizing the tools of science and engineering. In general, the term is used to refer to any branch of physics either developed in the early 20th century and onwards, or branches greatly influenced by early 20th century physics.

Modern physics can be considered consisting of classical physics, the Standard Model of physics and theoretical physics including quantum physics, relativity and more.

Low velocities and everyday distances are usually considered in the realm of classical physics.

The Standard Model of physics is based on laboratory observations from laboratories like CERN and other laboratories and does not include a theory for gravitation such as relativity or other purely theoretical or mathematical physics.

Modern physics, however, today also involves theoretical and extreme conditions represented by quantum effects and relativity typically involving distances comparable to atoms (roughly 10−9 m), while relativistic effects typically involve velocities comparable to the speed of light (roughly 3×108 m/s). In general, quantum and relativistic effects are believed to exist across all scales, although these effects can be very small in everyday life.