The Encyclopedia of Biophysics is envisioned both as an easily accessible source of information and as a route into the scientific literature. It consists of two parts, Systems and Techniques. In the Techniques sections, each of the wide range of methods which fall under the heading of Biophysics are explained in detail, together with the value and the limitations of the information each provides. Techniques covered range from diffraction (X-ray, electron and neutron), through a wide range of spectroscopic methods (X-ray, optical, EPR, NMR) to imaging (from electron microscopy to live cell imaging and MRI), as well as computational and simulation approaches.In the Systems sections, biophysical approaches to particular biological systems or problems ? from protein and nucleic acid structure to membranes, ion channels and receptors ? are described. These sections, which have an emphasis on the integration of the different techniques, therefore provide an entry into Biophysics from the biological more than from the technique-oriented physical/chemical direction. Thus the Encyclopedia is intended to provide a resource both for biophysicists interested in approaches outside their immediate sub-discipline and for people coming to biophysics from either the physical or biological direction. Each of the sections will include concise introductions to the major concepts and methods, and outlines of more specific topics, in each case with links to a limited number of carefully selected key reviews and/or papers in the scientific literature. There will also be short definitions explaining key terms. Extensive cross-referencing (hyperlinks in the online version) between different articles will allow access to related topics in a user-friendly manner and time-efficient manner, including hyperlinks to key articles in the scientific literature.