  Integral field, or 3D, spectroscopy is the technique of obtaining spectral
information over a two-dimensional, hopefully contiguous, field of view. While
there is some form of astronomical 3D spectroscopy at all wavelengths, there
has been a rapid increase in interest in optical and near-infrared 3D
spectroscopy. This has resulted in the deployment of a large variety of
integral-field spectrographs on most of the large optical/infrared telescopes.
The amount of IFU data available in observatory archives is large and growing
rapidly. The complications of treating IFU data as both imaging and
spectroscopy make it a special challenge for the virtual observatory. This
article describes the various techniques of optical and near-infrared
spectroscopy and some of the general needs and issues related to the handling
of 3D data by the virtual observatory.
