GATOS (GTC Astrophysical Transient Octuple-channel imaging Spectrograph) is a multi-channel imager and spectrograph capable of simultaneously obtaining images of the same field in 8 optical and near-infrared bands or alternatively performing spectroscopy covering the range between 3500 and 23500 Angstrom in a single shot at a resolving power of R ∼ 4000. State-of-the-art detectors envisioned for this instrument will have negligible readout times and be able to perform high-time-resolution observations. An integral-field mode covering the same range simultaneously will be a crucial element of the design. In its current design, the integral-field unit covers a field of 12" × 8" with 0.6" slitlets. Finally, we aim to include a unique spectropolarimetry unit that will give GTC the first broad-band spectropolarimeter on a 10 m class telescope. The design is an evolution of the OCTOCAM concept that was selected to be built at Gemini, and is now known as SCORPIO.