VESTA is a three-dimensional visualization system for both structural models and volumetric data such as electron and nuclear densities, Patterson functions, electrostatic potentials, and wave functions. VESTA represents crystal structures by ball-and-stick, space-filling, polyhedral, wireframe, stick, dot-surface, and thermal-ellipsoid models. A variety of crystal-chemical information is extractable from fractional coordinates, occupancies, and oxidation states of sites. Volumetric data are displayed as isosurfaces, bird's-eye views, and two-dimensional maps. Isosurfaces can be colored according to other physical quantities such as electrostatic potentials. Translucent isosurfaces and/or slices can be overlapped with a structural model. Collaboration with external programs enables the user to standardize crystal data, simulate X-ray and neutron powder diffraction patterns, and calculate site potentials and Madelung energies. Electron densities determined experimentally are convertible into their Laplacians and electronic-energy densities.