What Is Biophysics?

Biophysics is the field that uses the concepts, quantitative models and instruments of physics to explain how living systems work. Where a biologist might ask what a protein does, a biophysicist asks how it folds, how much energy it takes to change shape, how fast it moves, how strongly it binds a partner, and how those numbers add up to a function. The subject spans a very wide range of scales, from a single ion passing through a channel in a membrane, through proteins, nucleic acids and the machines they form, up to whole cells and tissues. The common thread is not a particular organism or molecule but a way of working: measure precisely, model mathematically, and ask what physical principle makes the observed behavior inevitable.

This guide is a discipline explainer in the same series as CASRAI’s guides to physics and biochemistry. It covers what biophysics studies, how it differs from its neighbors, its main subfields and methods, a short history, who funds it, which societies and journals anchor it, and how people train for it. It is an overview of a research enterprise, not a laboratory protocol, and it deliberately states only things that can be checked against primary sources.

What Biophysics Actually Studies

Because the field is defined by approach rather than subject matter, it is easiest to understand through the kinds of questions it asks:

• Structure. What is the three-dimensional arrangement of atoms in a protein, nucleic acid, membrane or large complex, and how does that arrangement explain function?
• Dynamics. Biological molecules are not rigid. Biophysics measures and models how they flex, switch between states, fold and unfold, and how quickly.
• Energetics and thermodynamics. How much free energy drives a binding event, a conformational change or an assembly process, and how do cells use energy gradients? See the CASRAI guide to thermodynamics for the underlying physics.
• Forces and mechanics. How do motor proteins generate force, how stiff is a strand of DNA, how do membranes bend, and how do cells sense mechanical cues?
• Electrical and signaling behavior. How do ion channels, transporters and membranes produce the electrical signals that nerves and muscles depend on?
• Physical limits and noise. How do small numbers of molecules and thermal fluctuations shape what a cell can reliably do?

Because of this orientation, biophysics tends to be quantitative and instrument-heavy. A typical project pairs a carefully controlled measurement with a mathematical or computational model, and treats disagreement between the two as the interesting result.

How Biophysics Relates to Neighboring Fields

The boundaries are matters of emphasis, and many researchers move between these areas during a career.

• Biochemistry asks what chemical reactions and molecules underlie life. Biophysics shares many of its tools but foregrounds physical principles, such as forces, energy landscapes and kinetics, over reaction mechanisms. CASRAI’s biochemistry guide covers the chemistry-first view.
• Molecular biology concentrates on information-carrying molecules and the machinery that copies and regulates them; see what molecular biology studies.
• Physics is the parent discipline for the methods and models. Some physicists work on living matter as a branch of condensed-matter or statistical physics, which is why funders describe a “physics of living systems” alongside molecular biophysics. See what physics studies.
• Structural biology is best seen as a large, methods-defined subfield of biophysics (and of biochemistry) devoted to determining and interpreting molecular structures. See also what crystallography is.
• Neuroscience draws on biophysics wherever it needs a quantitative account of how neurons generate and transmit signals; see what neuroscience studies.
• Biology more broadly supplies the systems under study; the CASRAI guide to biology and the map of the branches of science show where these fields sit relative to one another.

Major Subfields

Biophysicists usually identify with a subfield defined by scale or by method. Common ones include:

• Molecular and structural biophysics — structure, folding, stability and dynamics of proteins and nucleic acids and their assemblies.
• Membrane biophysics — lipid bilayers, membrane proteins, ion channels and transporters, and how membranes organize and deform.
• Single-molecule biophysics — observing or manipulating one molecule at a time to see behavior that ensemble averages hide.
• Cellular and mechanical biophysics — the cytoskeleton, cell motility, mechanotransduction and the physical organization of the cell interior.
• Computational and theoretical biophysics — molecular simulation, statistical-mechanical models and, increasingly, machine-learning methods for structure and dynamics.
• Systems and physics of living systems — physical principles of collective behavior, signaling networks and development at the level of cells and tissues.
• Biophysical imaging and instrumentation — developing the microscopes, spectrometers and force probes that make new measurements possible.

Core Methods

Methods are central to biophysics, and many of the field’s breakthroughs were instrument breakthroughs. The techniques below are the ones most often named in structural and molecular work; each is a specialty with its own training and facility requirements.

X-ray crystallography

X-ray crystallography determines atomic structures by diffracting X-rays from an ordered crystal of the molecule and reconstructing the electron density from the diffraction pattern. It was the method behind the first protein structures and remains a workhorse for well-behaved proteins that crystallize. Obtaining a diffracting crystal is often the hardest step, and many facilities rely on synchrotron beamlines. CASRAI covers the method in its X-ray crystallography guide, the general concept in what is crystallography, and where solved structures are deposited in the Protein Data Bank guide.

Cryo-electron microscopy (cryo-EM)

In cryo-EM, a sample is vitrified, meaning frozen so quickly that water forms a glass rather than ice crystals, and then imaged with an electron microscope. Thousands of individual particle images are computationally aligned and averaged to reconstruct a three-dimensional structure, without needing a crystal. The 2017 Nobel Prize in Chemistry went to Jacques Dubochet, Joachim Frank and Richard Henderson “for developing cryo-electron microscopy for the high-resolution structure determination of biomolecules in solution.” Cryo-EM is especially valuable for large complexes and membrane proteins that resist crystallization. The instruments are expensive and usually housed in shared facilities. See the dictionary entry for the cryo-EM microscope, the guide to the EMPIAR electron microscopy image archive, and the related transmission electron microscopy guide.

Nuclear magnetic resonance (NMR) spectroscopy

NMR measures the behavior of atomic nuclei in a strong magnetic field and can yield structural and dynamic information on molecules in solution, with no crystal required. It is particularly strong for characterizing motion, flexible or disordered regions, and interactions at specific atoms, and it has traditionally been applied most readily to smaller proteins and domains. NMR is a separate analytical tradition from the chemistry-lab uses described in CASRAI’s analytical chemistry guide, but the physical principles are shared.

Single-molecule methods

Single-molecule techniques watch or manipulate individual molecules rather than averaging over billions. Examples include single-molecule fluorescence and FRET, total internal reflection fluorescence, force spectroscopy with optical tweezers or atomic force microscopy, and electrophysiological recording from single ion channels. Three Nobel Prizes illustrate the range: the 1991 Nobel Prize in Physiology or Medicine to Erwin Neher and Bert Sakmann for their discoveries concerning the function of single ion channels in cells (the patch-clamp technique); the 2014 Nobel Prize in Chemistry for super-resolved fluorescence microscopy (Eric Betzig, Stefan Hell and William Moerner); and the 2018 Nobel Prize in Physics, half of which went to Arthur Ashkin for optical tweezers and their application to biological systems. CASRAI has guides to FRET microscopy, TIRF microscopy, super-resolution microscopy, FRAP and atomic force microscopy imaging modes.

Spectroscopy, scattering and other ensemble methods

Ensemble techniques remain essential because they are fast, quantitative and usable on samples that will not crystallize or image well. They include fluorescence and absorbance spectroscopy (see the fluorescence spectroscopy guide), light scattering (see dynamic light scattering), calorimetry for binding thermodynamics, and mass spectrometry for composition and interactions (see what a mass spectrometer is).

Computation and modeling

Molecular dynamics simulation, statistical-mechanical modeling and structure prediction complement experiment by proposing mechanisms and testing them against data. The 2024 Nobel Prize in Chemistry recognized computational protein design (David Baker) and protein structure prediction (Demis Hassabis and John Jumper), which has made computed structural models a routine starting point for experimental design. Predicted models are hypotheses to be tested, not substitutes for measurement. For the data side, see CASRAI’s guide to bioinformatics.

A Short History

Physical thinking about biology is old, but biophysics as an organized field took shape in the twentieth century. Structural work is the clearest thread: in 1962 the Nobel Prize in Chemistry went to Max Perutz and John Kendrew for the first structures of globular proteins (hemoglobin and myoglobin), established by X-ray crystallography. The Biophysical Society was formally founded in March 1957 after a national conference in Columbus, Ohio, in response to the growth of the field after the Second World War and concern that existing physiological societies had grown too large to serve biophysicists. Electrophysiology and single-channel recording matured through the 1970s and 1980s; single-molecule optics and force spectroscopy followed in the late twentieth century; and the cryo-EM “resolution revolution” of the 2010s moved a large part of structural biology away from crystals. Each step was driven by a new instrument, which is why access to instruments is such a prominent theme in biophysics funding.

Funders and Research Infrastructure

As with most laboratory sciences, funding determines what can be built and measured. In the United States, biophysics is supported mainly through two federal routes, and the answer to “who funds this?” depends on whether a project is framed around a biomedical question or a basic physical one.

• NIH, chiefly NIGMS. The National Institute of General Medical Sciences houses a Division of Biophysics, Biomedical Technology, and Computational Biosciences (BBCB), which includes a Biophysics Branch, a Biomedical Technology Branch and a Bioinformatics and Computational Biology Branch. NIGMS describes the Biophysics Branch as supporting research that applies quantitative principles and techniques to elucidate structures and structure-function relationships in fundamental biology, and says it continues to support structural biology using X-ray crystallography, NMR, cryo-EM and integrative or hybrid methods. NIGMS has also described programs to support cryo-EM facilities. Projects tied to a particular disease may instead fit a disease-focused NIH institute. For how payline and funding decisions work, see the dictionary entry on the NIGMS payline.
• NSF. Within the Division of Molecular and Cellular Biosciences (MCB), the Molecular Biophysics cluster focuses on the structure, dynamics and function of biomolecules and supramolecular assemblies, especially under physiological conditions. Separately, the Physics of Living Systems program, run through NSF’s physics directorate, targets theoretical and experimental work on the fundamental physical processes that living systems use, and the two programs have co-funded projects. See the dictionary entry for the National Science Foundation.

Other funders, including the Department of Energy (which operates national user facilities) and private foundations, also support parts of the field, but program names, solicitations and eligibility rules change. Anyone planning an application should check current guidance directly with NIGMS, NSF or the relevant foundation rather than rely on this summary.

Much biophysics also depends on shared resources. Cryo-EM microscopes, NMR magnets and synchrotron beamlines are too costly for individual labs, so access is arranged through core facilities and national user facilities, which in turn shapes budgets, scheduling and authorship decisions (see CASRAI’s guide to core facility staff authorship).

Societies, Journals and Data Resources

The Biophysical Society, based in the United States, is the main international society for the field. Its members, reported at over 7,000, work in academia, industry and government, and it holds an annual meeting that it describes as the largest gathering of biophysicists in the world. It publishes Biophysical Journal, established two years after the society was founded, and a newer open-access title, Biophysical Reports. Regional and international bodies also exist, including the European Biophysical Societies’ Association and the International Union for Pure and Applied Biophysics (IUPAB), and many researchers also belong to societies in adjacent areas such as biochemistry, crystallography or neuroscience.

Structural biophysics generates data that the community expects to be deposited publicly. Atomic models go to the Protein Data Bank (see the PDB guide), and raw cryo-EM images can be deposited in EMPIAR (see the EMPIAR guide).

Training and Career Paths

There is no single entry route, which is part of the field’s character. Undergraduates arrive from physics, chemistry, biology, biochemistry, engineering and mathematics, and many universities offer biophysics as a major, a track or a graduate program, often within a physics, chemistry, molecular biophysics or biomedical sciences department. Because the work needs both quantitative skills and wet-lab fluency, students usually have to fill gaps on one side: physicists learn to handle biological samples, and biologists learn calculus, statistics, programming and physical chemistry. Research careers typically run through a PhD and then postdoctoral training before an independent academic, industry or government laboratory position. Skills in instrumentation, data analysis and modeling also carry into biotechnology, pharmaceutical discovery, medical devices and data science, and into research roles that support shared instrument facilities.

From Biophysics to Research Administration

Biophysics is unusually exposed to the administrative side of research because its instruments are expensive and shared. Proposals must justify equipment and facility access, budgets must cover recharge fees, and projects must plan for sharing large data sets. CASRAI’s Research Methods hub collects methodology and laboratory guidance; the data management plan entry explains the planning document most funders now expect; and the NIH biosketch entry covers the personnel document required in NIH applications.

Frequently Asked Questions

What is biophysics in simple terms?

Biophysics is the use of physics, meaning its measurements, mathematics and ways of thinking about forces, energy and motion, to understand how biological molecules, cells and organisms function.

Is biophysics the same as biochemistry?

No, although they overlap heavily and share methods such as crystallography and spectroscopy. Biochemistry emphasizes the chemistry of life, including reactions, pathways and molecular composition. Biophysics emphasizes physical principles, including structure, forces, kinetics and energy landscapes, and often uses quantitative models. Many departments and journals cover both.

What techniques do biophysicists use?

Common ones are X-ray crystallography, cryo-electron microscopy, NMR spectroscopy, single-molecule fluorescence and force methods, patch-clamp electrophysiology, light scattering and calorimetry, mass spectrometry, and computational approaches such as molecular dynamics simulation. Which one fits depends on the size of the system, whether it can be crystallized and what question is being asked.

Is cryo-EM replacing X-ray crystallography?

Cryo-EM has become a leading method for large complexes and membrane proteins that are difficult to crystallize, but the methods are complementary rather than interchangeable. Crystallography remains widely used, and NMR, cryo-EM and crystallography are often combined in integrative approaches, as NIGMS notes in describing the structural biology it supports.

Who funds biophysics research?

In the United States, mainly the National Institutes of Health, particularly NIGMS and its Division of Biophysics, Biomedical Technology, and Computational Biosciences, and the National Science Foundation, through its Molecular Biophysics cluster in MCB and the Physics of Living Systems program. Other agencies and private foundations also contribute.

What is the Biophysical Society?

It is the professional society for biophysicists, formally founded in 1957. It runs a large annual meeting and publishes Biophysical Journal and Biophysical Reports.

What do you study to become a biophysicist?

There is no single path. Physics, chemistry, biology, biochemistry, engineering and mathematics backgrounds all lead into the field, usually followed by a PhD in biophysics or a related discipline and postdoctoral training for research careers. Quantitative training and hands-on laboratory experience are both valuable.