  IRIS is a near-infrared (0.84 to 2.4 microns) integral field spectrograph and
wide-field imager being developed for first light with the Thirty Meter (TMT).
It mounts to the advanced optics (AO) system NFIRAOS and has integrated
on-instrument wavefront sensors (OIWFS) to achieve diffraction-limited spatial
resolution at wavelengths longer than 1 micron. With moderate spectral
resolution (R ~4,000 - 8,000) and large bandpass over a continuous field of
view, IRIS will open new opportunities in virtually every area of astrophysical
science. It will be able to resolve surface features tens of kilometers across
Titan, while also mapping the distant galaxies at the scale of an individual
star forming region. This paper summarizes the entire design and capabilities,
and includes the results from the nearly completed preliminary design phase.
