Biophysics, the science that uses the principles and techniques of physics to study living organisms. In biophysics, such techniques as electrophoresis and electron microscopy are extensively used. (See Electrophoresis; Microscope, subtitle Kinds of Microscopes.)

Biophysicists study various molecules and particles that make up living cells, including nucleic acids, the molecules that control heredity. They investigate the effect of various types of radiation on living organisms, and such biological functions as the transmission of nerve impulses, contraction of muscles, and transport of materials in and out of cells. Some biophysicists specialize in analyzing the functions of living organisms by creating mathematical models or by using the principles of thermodynamics or statistical mechanics. The findings of biophysicists are applied primarily in medicine, especially to problems related to viral infections, cancer, heart disease, and space flight.

Biophysicists are trained in chemistry as well as in physics and biology. Most biophysicists are employed by research laboratories and universities.

Biophysics did not become established as a science until the 20th century, when newly developed instruments and techniques made advanced research possible.