The Spitzer IRAC/MUSYC Public Legacy Survey in the Extended Chandra Deep Field South (SIMPLE) consists of deep IRAC observations (several hours per pointing) covering the 0.5 x 0.5 deg area surrounding the GOODS CDF-South. This low-background region of the sky has by far the best supporting data of any cosmological survey field of comparable area, with deep observations from the X-rays to the thermal infrared.