Exploring the capabilities of IRIS: An AO-fed IFU and imager for the Thirty Meter Telescope Shelley Wright, UCB In the last decade there have been considerable advances in near-infrared astronomical integral field spectrographs designed for adaptive optic systems. These innovative spectrographs have made significant achievements and are stimulating the design of future instrumentation projects for the James Webb Space Telescope and Extremely Large Telescopes. I will present the current design, science cases, and predicted performance of the near-infrared integral field spectrograph and imager, IRIS (InfraRed Imaging Spectrograph), which is a first light instrument to take advantage of the diffraction-limit of the future Thirty Meter Telescope (TMT) on Mauna Kea, Hawaii. In particular, I will present simulated 3D IRIS data of resolved high-redshift star forming galaxies (1 < z < 5), illustrating the extraordinary potential of this instrument to probe the dynamics, assembly, and chemical abundances of galaxies in the early universe.